+ [jsfm] Support batch update styles and attributes

Add `setAttrs` and `setStyles` method on `Element.prototype` to support
batch update styles and attributes. This feature can be used in the DSL
framework to optimize performance.

html5/runtime/vdom/Element.js

@@ -298,6 +298,24 @@ export default class Element extends Node {
     }
   }
 
+  /**
+   * Set batched attributes.
+   * @param {object} batchedAttrs
+   * @param {boolean} silent
+   */
+  setAttrs (batchedAttrs, silent) {
+    // TODO: validate batched attributes
+    Object.assign(this.attr, batchedAttrs)
+    const taskCenter = getTaskCenter(this.docId)
+    if (!silent && taskCenter) {
+      taskCenter.send(
+        'dom',
+        { action: 'updateAttrs' },
+        [this.ref, batchedAttrs]
+      )
+    }
+  }
+
   /**
    * Set a style property, and decide whether the task should be send to native.
    * @param {string} key
@@ -321,6 +339,24 @@ export default class Element extends Node {
     }
   }
 
+  /**
+   * Set batched style properties.
+   * @param {object} batchedStyles
+   * @param {boolean} silent
+   */
+  setStyles (batchedStyles, silent) {
+    // TODO: validate batched styles
+    Object.assign(this.style, batchedStyles)
+    const taskCenter = getTaskCenter(this.docId)
+    if (!silent && taskCenter) {
+      taskCenter.send(
+        'dom',
+        { action: 'updateStyle' },
+        [this.ref, batchedStyles]
+      )
+    }
+  }
+
   /**
    * Set style properties from class.
    * @param {object} classStyle