diff --git a/Libraries/Utilities/Dimensions.js b/Libraries/Utilities/Dimensions.js
index a0fd7f308dc8bb..898c8cbe89580f 100644
--- a/Libraries/Utilities/Dimensions.js
+++ b/Libraries/Utilities/Dimensions.js
@@ -20,54 +20,17 @@ var invariant = require('fbjs/lib/invariant');
 var eventEmitter = new EventEmitter();
 var dimensionsInitialized = false;
 var dimensions = {};
-
-var dimensionsProvider: ?(() => {[key:string]: Object});
-
 class Dimensions {
-  static setProvider(value: () => {[key:string]: Object}): void {
-    dimensionsProvider = value;
-    dimensionsInitialized = false;
-    dimensions = {};
-  }
-
-  static getDimensions(): {[key:string]: Object} {
-    if (dimensionsInitialized) {
-      return dimensions;
-    }
-
-    // We calculate the window dimensions in JS so that we don't encounter loss of
-    // precision in transferring the dimensions (which could be non-integers) over
-    // the bridge.
-    const dims = (dimensionsProvider || defaultDimProvider)();
-    const result = Dimensions.updateDimensions(dims);
-    RCTDeviceEventEmitter.addListener('didUpdateDimensions', function(update) {
-      Dimensions.updateDimensions(update);
-    });
-    return result;
-  }
-
   /**
-   * Initial dimensions are set before `runApplication` is called so they should
-   * be available before any other require's are run, but may be updated later.
-   *
-   * Note: Although dimensions are available immediately, they may change (e.g
-   * due to device rotation) so any rendering logic or styles that depend on
-   * these constants should try to call this function on every render, rather
-   * than caching the value (for example, using inline styles rather than
-   * setting a value in a `StyleSheet`).
-   *
-   * Example: `var {height, width} = Dimensions.get('window');`
+   * This should only be called from native code by sending the
+   * didUpdateDimensions event.
    *
-   * @param {string} dim Name of dimension as defined when calling `set`.
-   * @returns {Object?} Value for the dimension.
+   * @param {object} dims Simple string-keyed object of dimensions to set
    */
-  static get(dim: string): Object {
-    const dims = Dimensions.getDimensions();
-    invariant(dims[dim], 'No dimension set for key ' + dim);
-    return dims[dim];
-  }
-
-  static updateDimensions(dims: ?{[key:string]: Object}): {[key:string]: Object} {
+  static set(dims: {[key:string]: any}): void {
+    // We calculate the window dimensions in JS so that we don't encounter loss of
+    // precision in transferring the dimensions (which could be non-integers) over
+    // the bridge.
     if (dims && dims.windowPhysicalPixels) {
       // parse/stringify => Clone hack
       dims = JSON.parse(JSON.stringify(dims));
@@ -108,7 +71,26 @@ class Dimensions {
     } else {
       dimensionsInitialized = true;
     }
-    return dimensions;
+  }
+
+  /**
+   * Initial dimensions are set before `runApplication` is called so they should
+   * be available before any other require's are run, but may be updated later.
+   *
+   * Note: Although dimensions are available immediately, they may change (e.g
+   * due to device rotation) so any rendering logic or styles that depend on
+   * these constants should try to call this function on every render, rather
+   * than caching the value (for example, using inline styles rather than
+   * setting a value in a `StyleSheet`).
+   *
+   * Example: `var {height, width} = Dimensions.get('window');`
+   *
+   * @param {string} dim Name of dimension as defined when calling `set`.
+   * @returns {Object?} Value for the dimension.
+   */
+  static get(dim: string): Object {
+    invariant(dimensions[dim], 'No dimension set for key ' + dim);
+    return dimensions[dim];
   }
 
   /**
@@ -145,8 +127,20 @@ class Dimensions {
   }
 }
 
-function defaultDimProvider(): {[key:string]: Object} {
-  return require('DeviceInfo').Dimensions;
+let dims: ?{[key: string]: any} = global.nativeExtensions && global.nativeExtensions.DeviceInfo && global.nativeExtensions.DeviceInfo.Dimensions;
+let nativeExtensionsEnabled = true;
+if (!dims) {
+  const DeviceInfo = require('DeviceInfo');
+  dims = DeviceInfo.Dimensions;
+  nativeExtensionsEnabled = false;
+}
+
+invariant(dims, 'Either DeviceInfo native extension or DeviceInfo Native Module must be registered');
+Dimensions.set(dims);
+if (!nativeExtensionsEnabled) {
+  RCTDeviceEventEmitter.addListener('didUpdateDimensions', function(update) {
+    Dimensions.set(update);
+  });
 }
 
 module.exports = Dimensions;
diff --git a/React/CxxBridge/RCTCxxBridge.mm b/React/CxxBridge/RCTCxxBridge.mm
index 72ad763f5c6acd..1fbb2fd43032d7 100644
--- a/React/CxxBridge/RCTCxxBridge.mm
+++ b/React/CxxBridge/RCTCxxBridge.mm
@@ -339,6 +339,7 @@ - (void)start
   #if RCT_PROFILE
         ("StartSamplingProfilerOnInit", (bool)self.devSettings.startSamplingProfilerOnLaunch)
   #endif
+         , nullptr
       ));
     }
   } else {
diff --git a/ReactAndroid/src/main/java/com/facebook/react/modules/deviceinfo/DeviceInfoModule.java b/ReactAndroid/src/main/java/com/facebook/react/modules/deviceinfo/DeviceInfoModule.java
index dec707a8506b4f..d6b43bf4b795a4 100644
--- a/ReactAndroid/src/main/java/com/facebook/react/modules/deviceinfo/DeviceInfoModule.java
+++ b/ReactAndroid/src/main/java/com/facebook/react/modules/deviceinfo/DeviceInfoModule.java
@@ -58,7 +58,7 @@ public String getName() {
     HashMap<String, Object> constants = new HashMap<>();
     constants.put(
         "Dimensions",
-        getDimensionsConstants());
+        DisplayMetricsHolder.getDisplayMetricsMap(mFontScale));
     return constants;
   }
 
@@ -90,31 +90,6 @@ public void emitUpdateDimensionsEvent() {
 
     mReactApplicationContext
         .getJSModule(DeviceEventManagerModule.RCTDeviceEventEmitter.class)
-        .emit("didUpdateDimensions", getDimensionsConstants());
-  }
-
-  private WritableMap getDimensionsConstants() {
-    DisplayMetrics windowDisplayMetrics = DisplayMetricsHolder.getWindowDisplayMetrics();
-    DisplayMetrics screenDisplayMetrics = DisplayMetricsHolder.getScreenDisplayMetrics();
-
-    WritableMap windowDisplayMetricsMap = Arguments.createMap();
-    windowDisplayMetricsMap.putInt("width", windowDisplayMetrics.widthPixels);
-    windowDisplayMetricsMap.putInt("height", windowDisplayMetrics.heightPixels);
-    windowDisplayMetricsMap.putDouble("scale", windowDisplayMetrics.density);
-    windowDisplayMetricsMap.putDouble("fontScale", mFontScale);
-    windowDisplayMetricsMap.putDouble("densityDpi", windowDisplayMetrics.densityDpi);
-
-    WritableMap screenDisplayMetricsMap = Arguments.createMap();
-    screenDisplayMetricsMap.putInt("width", screenDisplayMetrics.widthPixels);
-    screenDisplayMetricsMap.putInt("height", screenDisplayMetrics.heightPixels);
-    screenDisplayMetricsMap.putDouble("scale", screenDisplayMetrics.density);
-    screenDisplayMetricsMap.putDouble("fontScale", mFontScale);
-    screenDisplayMetricsMap.putDouble("densityDpi", screenDisplayMetrics.densityDpi);
-
-    WritableMap dimensionsMap = Arguments.createMap();
-    dimensionsMap.putMap("windowPhysicalPixels", windowDisplayMetricsMap);
-    dimensionsMap.putMap("screenPhysicalPixels", screenDisplayMetricsMap);
-
-    return dimensionsMap;
+        .emit("didUpdateDimensions", DisplayMetricsHolder.getDisplayMetricsMap(mFontScale));
   }
 }
diff --git a/ReactAndroid/src/main/java/com/facebook/react/uimanager/BUCK b/ReactAndroid/src/main/java/com/facebook/react/uimanager/BUCK
index 08e25d2c55f1f2..563bbe479a32b5 100644
--- a/ReactAndroid/src/main/java/com/facebook/react/uimanager/BUCK
+++ b/ReactAndroid/src/main/java/com/facebook/react/uimanager/BUCK
@@ -2,13 +2,17 @@ load("//ReactNative:DEFS", "rn_android_library", "YOGA_TARGET", "react_native_de
 
 rn_android_library(
     name = "uimanager",
-    srcs = glob([
-        "*.java",
-        "debug/*.java",
-        "events/*.java",
-        "layoutanimation/*.java",
-    ]),
+    srcs = glob(
+        [
+            "*.java",
+            "debug/*.java",
+            "events/*.java",
+            "layoutanimation/*.java",
+        ],
+        excludes = ["DisplayMetricsHolder.java"],
+    ),
     exported_deps = [
+        ":DisplayMetrics",
         react_native_dep("third-party/java/jsr-305:jsr-305"),
     ],
     provided_deps = [
@@ -21,6 +25,7 @@ rn_android_library(
     ],
     deps = [
         YOGA_TARGET,
+        ":DisplayMetrics",
         react_native_dep("java/com/facebook/systrace:systrace"),
         react_native_dep("libraries/fbcore/src/main/java/com/facebook/common/logging:logging"),
         react_native_dep("third-party/java/infer-annotations:infer-annotations"),
@@ -38,3 +43,19 @@ rn_android_library(
         react_native_target("res:uimanager"),
     ],
 )
+
+rn_android_library(
+    name = "DisplayMetrics",
+    srcs = glob([
+        "DisplayMetricsHolder.java",
+    ]),
+    required_for_source_only_abi = True,
+    visibility = [
+        "PUBLIC",
+    ],
+    deps = [
+        react_native_dep("third-party/java/infer-annotations:infer-annotations"),
+        react_native_dep("third-party/java/jsr-305:jsr-305"),
+        react_native_target("java/com/facebook/react/bridge:bridge"),
+    ],
+)
diff --git a/ReactAndroid/src/main/java/com/facebook/react/uimanager/DisplayMetricsHolder.java b/ReactAndroid/src/main/java/com/facebook/react/uimanager/DisplayMetricsHolder.java
index 04c26d8a23873a..a8d130ca621aa9 100644
--- a/ReactAndroid/src/main/java/com/facebook/react/uimanager/DisplayMetricsHolder.java
+++ b/ReactAndroid/src/main/java/com/facebook/react/uimanager/DisplayMetricsHolder.java
@@ -21,6 +21,7 @@
 import android.view.WindowManager;
 
 import com.facebook.infer.annotation.Assertions;
+import com.facebook.react.bridge.WritableNativeMap;
 
 /**
  * Holds an instance of the current DisplayMetrics so we don't have to thread it through all the
@@ -104,4 +105,26 @@ public static void setScreenDisplayMetrics(DisplayMetrics screenDisplayMetrics)
   public static DisplayMetrics getScreenDisplayMetrics() {
     return sScreenDisplayMetrics;
   }
+
+  public static WritableNativeMap getDisplayMetricsMap(double fontScale) {
+    Assertions.assertNotNull(
+        sWindowDisplayMetrics != null || sScreenDisplayMetrics != null,
+        "DisplayMetricsHolder must be initialized with initDisplayMetricsIfNotInitialized or initDisplayMetrics");
+    final WritableNativeMap result = new WritableNativeMap();
+    result.putMap("windowPhysicalPixels", getPhysicalPixelsMap(sWindowDisplayMetrics, fontScale));
+    result.putMap("screenPhysicalPixels", getPhysicalPixelsMap(sScreenDisplayMetrics, fontScale));
+
+    return result;
+  }
+
+  private static WritableNativeMap getPhysicalPixelsMap(DisplayMetrics displayMetrics, double fontScale) {
+    final WritableNativeMap result = new WritableNativeMap();
+    result.putInt("width", displayMetrics.widthPixels);
+    result.putInt("height", displayMetrics.heightPixels);
+    result.putDouble("scale", displayMetrics.density);
+    result.putDouble("fontScale", fontScale);
+    result.putDouble("densityDpi", displayMetrics.densityDpi);
+    return result;
+  }
+
 }
diff --git a/ReactAndroid/src/main/jni/react/jni/AndroidJSCFactory.cpp b/ReactAndroid/src/main/jni/react/jni/AndroidJSCFactory.cpp
index 0aba406fc24b86..ed551a61a2b590 100644
--- a/ReactAndroid/src/main/jni/react/jni/AndroidJSCFactory.cpp
+++ b/ReactAndroid/src/main/jni/react/jni/AndroidJSCFactory.cpp
@@ -90,9 +90,9 @@ void injectJSCExecutorAndroidPlatform() {
 }
 
 std::unique_ptr<JSExecutorFactory> makeAndroidJSCExecutorFactory(
-    const folly::dynamic& jscConfig) {
+    const folly::dynamic& jscConfig, std::function<folly::dynamic(const std::string&)> nativeExtensionsProvider) {
   detail::injectJSCExecutorAndroidPlatform();
-  return folly::make_unique<JSCExecutorFactory>(std::move(jscConfig));
+  return folly::make_unique<JSCExecutorFactory>(std::move(jscConfig), std::move(nativeExtensionsProvider));
 }
 
 }
diff --git a/ReactAndroid/src/main/jni/react/jni/AndroidJSCFactory.h b/ReactAndroid/src/main/jni/react/jni/AndroidJSCFactory.h
index 3bc5052978aea7..e1e782145c91e8 100644
--- a/ReactAndroid/src/main/jni/react/jni/AndroidJSCFactory.h
+++ b/ReactAndroid/src/main/jni/react/jni/AndroidJSCFactory.h
@@ -23,7 +23,7 @@ void injectJSCExecutorAndroidPlatform();
 }
 
 std::unique_ptr<JSExecutorFactory> makeAndroidJSCExecutorFactory(
-    const folly::dynamic& jscConfig);
+    const folly::dynamic& jscConfig, std::function<folly::dynamic(const std::string&)> nativeExtensionsProvider);
 
 }
 }
diff --git a/ReactAndroid/src/main/jni/react/jni/OnLoad.cpp b/ReactAndroid/src/main/jni/react/jni/OnLoad.cpp
index 9804be9caadd4a..ec97e56e5b1d02 100644
--- a/ReactAndroid/src/main/jni/react/jni/OnLoad.cpp
+++ b/ReactAndroid/src/main/jni/react/jni/OnLoad.cpp
@@ -38,7 +38,7 @@ class JSCJavaScriptExecutorHolder : public HybridClass<JSCJavaScriptExecutorHold
   static constexpr auto kJavaDescriptor = "Lcom/facebook/react/bridge/JSCJavaScriptExecutor;";
 
   static local_ref<jhybriddata> initHybrid(alias_ref<jclass>, ReadableNativeMap* jscConfig) {
-    return makeCxxInstance(makeAndroidJSCExecutorFactory(jscConfig->consume()));
+    return makeCxxInstance(makeAndroidJSCExecutorFactory(jscConfig->consume(), nullptr));
   }
 
   static void registerNatives() {
diff --git a/ReactCommon/cxxreact/JSCExecutor.cpp b/ReactCommon/cxxreact/JSCExecutor.cpp
index 09452f153b932b..a28b99e92126df 100644
--- a/ReactCommon/cxxreact/JSCExecutor.cpp
+++ b/ReactCommon/cxxreact/JSCExecutor.cpp
@@ -115,16 +115,18 @@ namespace facebook {
 
     std::unique_ptr<JSExecutor> JSCExecutorFactory::createJSExecutor(
                                                                      std::shared_ptr<ExecutorDelegate> delegate, std::shared_ptr<MessageQueueThread> jsQueue) {
-      return folly::make_unique<JSCExecutor>(delegate, jsQueue, m_jscConfig);
+      return folly::make_unique<JSCExecutor>(delegate, jsQueue, m_jscConfig, m_nativeExtensionsProvider);
     }
 
     JSCExecutor::JSCExecutor(std::shared_ptr<ExecutorDelegate> delegate,
                              std::shared_ptr<MessageQueueThread> messageQueueThread,
-                             const folly::dynamic& jscConfig) throw(JSException) :
+                             const folly::dynamic& jscConfig,
+                             std::function<folly::dynamic(const std::string &)> nativeExtensionsProvider) throw(JSException) :
     m_delegate(delegate),
     m_messageQueueThread(messageQueueThread),
     m_nativeModules(delegate ? delegate->getModuleRegistry() : nullptr),
-    m_jscConfig(jscConfig) {
+    m_jscConfig(jscConfig),
+    m_nativeExtensionsProvider(nativeExtensionsProvider) {
       initOnJSVMThread();
 
       {
@@ -132,6 +134,8 @@ namespace facebook {
         installGlobalProxy(m_context, "nativeModuleProxy",
                            exceptionWrapMethod<&JSCExecutor::getNativeModule>());
       }
+      installGlobalProxy(m_context, "nativeExtensions",
+                         exceptionWrapMethod<&JSCExecutor::getNativeExtension>());
     }
 
     JSCExecutor::~JSCExecutor() {
@@ -632,8 +636,8 @@ namespace facebook {
       return String::adopt(m_context, jsString);
 #else
       return script->isAscii()
-      ? String::createExpectingAscii(m_context, script->c_str(), script->size())
-      : String(m_context, script->c_str());
+          ? String::createExpectingAscii(m_context, script->c_str(), script->size())
+          : String(m_context, script->c_str());
 #endif
     }
 
@@ -677,6 +681,14 @@ namespace facebook {
       return m_nativeModules.getModule(m_context, propertyName);
     }
 
+    JSValueRef JSCExecutor::getNativeExtension(JSObjectRef object, JSStringRef propertyName) {
+      if (m_nativeExtensionsProvider) {
+        folly::dynamic value = m_nativeExtensionsProvider(String::ref(m_context, propertyName).str());
+        return Value::fromDynamic(m_context, std::move(value));
+      }
+      return JSC_JSValueMakeUndefined(m_context);
+    }
+
     JSValueRef JSCExecutor::nativeRequire(
                                           size_t argumentCount,
                                           const JSValueRef arguments[]) {
diff --git a/ReactCommon/cxxreact/JSCExecutor.h b/ReactCommon/cxxreact/JSCExecutor.h
index 66c101c5362d9f..258697af5c9587 100644
--- a/ReactCommon/cxxreact/JSCExecutor.h
+++ b/ReactCommon/cxxreact/JSCExecutor.h
@@ -27,14 +27,15 @@ class RAMBundleRegistry;
 
 class RN_EXPORT JSCExecutorFactory : public JSExecutorFactory {
 public:
-  JSCExecutorFactory(const folly::dynamic& jscConfig) :
-    m_jscConfig(jscConfig) {}
+  JSCExecutorFactory(const folly::dynamic& jscConfig, std::function<folly::dynamic(const std::string &)> provider) :
+    m_jscConfig(jscConfig), m_nativeExtensionsProvider(provider) {}
   std::unique_ptr<JSExecutor> createJSExecutor(
     std::shared_ptr<ExecutorDelegate> delegate,
     std::shared_ptr<MessageQueueThread> jsQueue) override;
 private:
   std::string m_cacheDir;
   folly::dynamic m_jscConfig;
+  std::function<folly::dynamic(const std::string &)> m_nativeExtensionsProvider;
 };
 
 template<typename T>
@@ -58,7 +59,8 @@ class RN_EXPORT JSCExecutor : public JSExecutor, public PrivateDataBase {
    */
   explicit JSCExecutor(std::shared_ptr<ExecutorDelegate> delegate,
                        std::shared_ptr<MessageQueueThread> messageQueueThread,
-                       const folly::dynamic& jscConfig) throw(JSException);
+                       const folly::dynamic& jscConfig,
+                       std::function<folly::dynamic(const std::string &)> nativeExtensionsProvider) throw(JSException);
   ~JSCExecutor() override;
 
   virtual void loadApplicationScript(
@@ -112,6 +114,7 @@ class RN_EXPORT JSCExecutor : public JSExecutor, public PrivateDataBase {
   JSCNativeModules m_nativeModules;
   folly::dynamic m_jscConfig;
   std::once_flag m_bindFlag;
+  std::function<folly::dynamic(const std::string &)> m_nativeExtensionsProvider;
 
   folly::Optional<Object> m_invokeCallbackAndReturnFlushedQueueJS;
   folly::Optional<Object> m_callFunctionReturnFlushedQueueJS;
@@ -134,7 +137,9 @@ class RN_EXPORT JSCExecutor : public JSExecutor, public PrivateDataBase {
 
   template<JSValueRef (JSCExecutor::*method)(size_t, const JSValueRef[])>
   void installNativeHook(const char* name);
+
   JSValueRef getNativeModule(JSObjectRef object, JSStringRef propertyName);
+  JSValueRef getNativeExtension(JSObjectRef object, JSStringRef propertyName);
 
   JSValueRef nativeRequire(
       size_t argumentCount,