Back out 5d997f85c1b9 (Bug 639179 Part 1) due to mobile unittest orange. CLOSED TREE

mobile/chrome/content/input.js

@@ -328,8 +328,11 @@ MouseModule.prototype = {
       if (dragData.isPan()) {
         // Only pan when mouse event isn't part of a click. Prevent jittering on tap.
         this._kinetic.addData(sX - dragData.prevPanX, sY - dragData.prevPanY);
-        this._dragBy(this.dX, this.dY);
-        // dragBy will reset dX and dY values to 0.
+        if (!this._waitingForPaint) {
+          this._dragBy(this.dX, this.dY);
+          this.dX = 0;
+          this.dY = 0;
+        }
 
         // Let everyone know when mousemove begins a pan
         if (!oldIsPan && dragData.isPan()) {
@@ -391,16 +394,11 @@ MouseModule.prototype = {
    * the dragger of dragMove()s.
    */
   _dragBy: function _dragBy(dX, dY, aIsKinetic) {
-    let dragged = true;
-    if (!this._waitingForPaint || aIsKinetic) {
-      let dragData = this._dragData;
-      dragged = this._dragger.dragMove(dX, dY, this._targetScrollInterface, aIsKinetic);
-      if (dragged && !this._waitingForPaint) {
-        this._waitingForPaint = true;
-        mozRequestAnimationFrame(this);
-      }
-      this.dX = 0;
-      this.dY = 0;
+    let dragData = this._dragData;
+    let dragged = this._dragger.dragMove(dX, dY, this._targetScrollInterface, aIsKinetic);
+    if (dragged && !this._waitingForPaint) {
+      this._waitingForPaint = true;
+      mozRequestAnimationFrame(this);
     }
     return dragged;
   },