diff --git a/lib/build.js b/lib/build.js
index 190b37608638..74e7a43b8425 100644
--- a/lib/build.js
+++ b/lib/build.js
@@ -18,19 +18,8 @@ const touchOverriddenFiles = () => {
     return true
   }
 
-  const walkSync = (dir, filelist = []) => {
-    fs.readdirSync(dir).forEach(file => {
-      if (fs.statSync(path.join(dir, file)).isDirectory()) {
-        filelist = walkSync(path.join(dir, file), filelist)
-      } else if (applyFileFilter(file)) {
-        filelist = filelist.concat(path.join(dir, file))
-      }
-    })
-    return filelist
-  }
-
   const chromiumSrcDir = path.join(config.srcDir, 'brave', 'chromium_src')
-  var sourceFiles = walkSync(chromiumSrcDir)
+  var sourceFiles = util.walkSync(chromiumSrcDir, applyFileFilter)
 
   // Touch original files by updating mtime.
   const chromiumSrcDirLen = chromiumSrcDir.length
@@ -63,19 +52,8 @@ const touchOverriddenVectorIconFiles = () => {
     return true
   }
 
-  const walkSync = (dir, filelist = []) => {
-    fs.readdirSync(dir).forEach(file => {
-      if (fs.statSync(path.join(dir, file)).isDirectory()) {
-        filelist = walkSync(path.join(dir, file), filelist)
-      } else if (applyFileFilter(file)) {
-        filelist = filelist.concat(path.join(dir, file))
-      }
-    })
-    return filelist
-  }
-
   const braveVectorIconsDir = path.join(config.srcDir, 'brave', 'vector_icons')
-  var braveVectorIconFiles = walkSync(braveVectorIconsDir)
+  var braveVectorIconFiles = util.walkSync(braveVectorIconsDir, applyFileFilter)
 
   // Touch original files by updating mtime.
   const braveVectorIconsDirLen = braveVectorIconsDir.length
diff --git a/lib/util.js b/lib/util.js
index c82a0b7d7f8f..b97dc3be96d9 100644
--- a/lib/util.js
+++ b/lib/util.js
@@ -66,47 +66,79 @@ const util = {
     const braveBrowserDir = path.join(config.projects['brave-core'].dir, 'browser')
     const braveAppVectorIconsDir = path.join(config.projects['brave-core'].dir, 'vector_icons', 'chrome', 'app')
 
-    // The following 3 entries we map to the same name, not the chromium equivalent name for copying back
-    autoGeneratedBraveToChromiumMapping[path.join(braveAppDir, 'brave_strings.grd')] = path.join(chromeAppDir, 'brave_strings.grd')
-    autoGeneratedBraveToChromiumMapping[path.join(braveAppDir, 'settings_brave_strings.grdp')] = path.join(chromeAppDir, 'settings_brave_strings.grdp')
-    autoGeneratedBraveToChromiumMapping[path.join(braveAppDir, 'components_brave_strings.grd')] = path.join(config.srcDir, 'components', 'components_brave_strings.grd')
+    let fileMap = {}
+    fileMap[path.join(braveAppDir, 'brave_strings.grd')] = path.join(chromeAppDir, 'brave_strings.grd')
+    fileMap[path.join(braveAppDir, 'settings_brave_strings.grdp')] = path.join(chromeAppDir, 'settings_brave_strings.grdp')
+    fileMap[path.join(braveAppDir, 'components_brave_strings.grd')] = path.join(config.srcDir, 'components', 'components_brave_strings.grd')
 
-    // Copy each grd back to Chromium src dir
-    Object.entries(autoGeneratedBraveToChromiumMapping).forEach(([bravePath, chromiumPath]) =>
-      fs.copySync(bravePath, chromiumPath))
 
     // Copy xtb files for:
     // brave/app/resources/chromium_strings*.xtb
     // brave/app/strings/components_chromium_strings*.xtb
     // brave/app/resources/generated_resoruces*.xtb
-    fs.copySync(path.join(braveAppDir, 'resources'), path.join(chromeAppDir, 'resources'))
-    fs.copySync(path.join(braveAppDir, 'strings'), path.join(chromeComponentsDir, 'strings'))
+    fileMap[path.join(braveAppDir, 'resources')] = path.join(chromeAppDir, 'resources')
+    fileMap[path.join(braveAppDir, 'strings')] = path.join(chromeComponentsDir, 'strings')
 
-    fs.copySync(path.join(braveAppDir, 'theme', 'brave'), path.join(chromeAppDir, 'theme', 'brave'))
-    fs.copySync(path.join(braveAppDir, 'theme', 'default_100_percent', 'brave'), path.join(chromeAppDir, 'theme', 'default_100_percent', 'brave'))
-    fs.copySync(path.join(braveAppDir, 'theme', 'default_200_percent', 'brave'), path.join(chromeAppDir, 'theme', 'default_200_percent', 'brave'))
+    fileMap[path.join(braveAppDir, 'theme', 'brave')] = path.join(chromeAppDir, 'theme', 'brave')
+    fileMap[path.join(braveAppDir, 'theme', 'default_100_percent', 'brave')] = path.join(chromeAppDir, 'theme', 'default_100_percent', 'brave')
+    fileMap[path.join(braveAppDir, 'theme', 'default_200_percent', 'brave')] = path.join(chromeAppDir, 'theme', 'default_200_percent', 'brave')
     // By overwriting, we don't need to modify some grd files.
-    fs.copySync(path.join(braveAppDir, 'theme', 'brave'), path.join(chromeAppDir, 'theme', 'chromium'))
-    fs.copySync(path.join(braveAppDir, 'theme', 'default_100_percent', 'brave'), path.join(chromeAppDir, 'theme', 'default_100_percent', 'chromium'))
-    fs.copySync(path.join(braveAppDir, 'theme', 'default_200_percent', 'brave'), path.join(chromeAppDir, 'theme', 'default_200_percent', 'chromium'))
-    fs.copySync(path.join(braveComponentsDir, 'resources', 'default_100_percent', 'brave'), path.join(chromeComponentsDir, 'resources', 'default_100_percent', 'chromium'))
-    fs.copySync(path.join(braveComponentsDir, 'resources', 'default_200_percent', 'brave'), path.join(chromeComponentsDir, 'resources', 'default_200_percent', 'chromium'))
-    fs.copySync(path.join(braveAppVectorIconsDir, 'vector_icons', 'brave'), path.join(chromeAppDir, 'vector_icons', 'brave'))
-    fs.copySync(path.join(braveResourcesDir, 'settings', 'brave_page_visibility.js'), path.join(chromeResourcesDir, 'settings', 'brave_page_visibility.js'))
-    fs.copySync(path.join(braveResourcesDir, 'settings', 'brave_appearance_page'), path.join(chromeResourcesDir, 'settings', 'brave_appearance_page'))
+    fileMap[path.join(braveAppDir, 'theme', 'brave')] = path.join(chromeAppDir, 'theme', 'chromium')
+    fileMap[path.join(braveAppDir, 'theme', 'default_100_percent', 'brave')] = path.join(chromeAppDir, 'theme', 'default_100_percent', 'chromium')
+    fileMap[path.join(braveAppDir, 'theme', 'default_200_percent', 'brave')] = path.join(chromeAppDir, 'theme', 'default_200_percent', 'chromium')
+    fileMap[path.join(braveComponentsDir, 'resources', 'default_100_percent', 'brave')] = path.join(chromeComponentsDir, 'resources', 'default_100_percent', 'chromium')
+    fileMap[path.join(braveComponentsDir, 'resources', 'default_200_percent', 'brave')] = path.join(chromeComponentsDir, 'resources', 'default_200_percent', 'chromium')
+    fileMap[path.join(braveAppVectorIconsDir, 'vector_icons', 'brave')] = path.join(chromeAppDir, 'vector_icons', 'brave')
+    fileMap[path.join(braveResourcesDir, 'settings', 'brave_page_visibility.js')] = path.join(chromeResourcesDir, 'settings', 'brave_page_visibility.js')
+    fileMap[path.join(braveResourcesDir, 'settings', 'brave_appearance_page')] = path.join(chromeResourcesDir, 'settings', 'brave_appearance_page')
 
     if (process.platform === 'darwin') {
       // Copy proper mac app icon for channel to chrome/app/theme/mac/app.icns.
       // Each channel's app icons are stored in brave/app/theme/$channel/app.icns.
       // With this copying, we don't need to modify chrome/BUILD.gn for this.
-      fs.copySync(path.join(braveAppDir, 'theme', 'brave', 'mac', config.channel, 'app.icns'),
-                  path.join(chromeAppDir, 'theme', 'brave', 'mac', 'app.icns'))
+      fileMap[path.join(braveAppDir, 'theme', 'brave', 'mac', config.channel, 'app.icns')] =
+                  path.join(chromeAppDir, 'theme', 'brave', 'mac', 'app.icns')
 
       // Copy branding file
       let branding_file_name = 'BRANDING'
       if (config.channel)
         branding_file_name = branding_file_name + '.' + config.channel
-      fs.copySync(path.join(braveAppDir, 'theme', 'brave', branding_file_name), path.join(chromeAppDir, 'theme', 'brave', 'BRANDING'))
+      fileMap[path.join(braveAppDir, 'theme', 'brave', branding_file_name)] =
+          path.join(chromeAppDir, 'theme', 'brave', 'BRANDING')
+    }
+
+    for (source in fileMap) {
+      let sourceFiles = []
+      const output = fileMap[source]
+
+      // get all the files if source if a directory
+      if (fs.statSync(source).isDirectory()) {
+        sourceFiles = util.walkSync(source)
+      } else {
+        sourceFiles = [source]
+      }
+
+      for (var i in sourceFiles) {
+        const sourceFile = sourceFiles[i]
+        let destinationFile = output
+        if (fs.statSync(destinationFile).isDirectory()) {
+          destinationFile = path.join(destinationFile, path.basename(sourceFile))
+        }
+
+        // The destination file might be newer when updating chromium so
+        // we check for an exact match on the timestamp. We use seconds instead
+        // of ms because utimesSync doesn't set the times with ms precision
+        if (!fs.existsSync(destinationFile) ||
+            Math.floor(new Date(fs.statSync(sourceFile).mtimeMs).getTime() / 1000) !=
+            Math.floor(new Date(fs.statSync(destinationFile).mtimeMs).getTime() / 1000)) {
+          fs.copySync(sourceFile, destinationFile)
+          // can't set the date in the past so update the source file
+          // to match the newly copied destionation file
+          const date = fs.statSync(destinationFile).mtime
+          fs.utimesSync(sourceFile, date, date)
+          console.log(sourceFile + ' copied to ' + destinationFile)
+        }
+      }
     }
   },
 
@@ -179,6 +211,17 @@ const util = {
       args += arg + '=' + val + ' '
     }
     return args.replace(/"/g,'\\"')
+  },
+
+  walkSync: (dir, filter = null, filelist = []) => {
+    fs.readdirSync(dir).forEach(file => {
+      if (fs.statSync(path.join(dir, file)).isDirectory()) {
+        filelist = util.walkSync(path.join(dir, file), filter, filelist)
+      } else if (!filter || filter.call(null, file)) {
+        filelist = filelist.concat(path.join(dir, file))
+      }
+    })
+    return filelist
   }
 }