Add source to hover events for VR

Hover events don't get processed if the source is not set.
This change shouldn't affect scrolling performance metrics.

Bug: 880879, 877580
Change-Id: I07ae28fcfdebfee77eab57e5659d1150745b6e9a
Reviewed-on: https://chromium-review.googlesource.com/1207651Reviewed-by: Jinsuk Kim <jinsukkim@chromium.org>
Commit-Queue: Aldo Culquicondor <acondor@chromium.org>
Cr-Commit-Position: refs/heads/master@{#589151}

content/public/android/java/src/org/chromium/content/browser/MotionEventSynthesizerImpl.java

@@ -4,6 +4,7 @@
 
 package org.chromium.content.browser;
 
+import android.view.InputDevice;
 import android.view.MotionEvent;
 import android.view.MotionEvent.PointerCoords;
 import android.view.MotionEvent.PointerProperties;
@@ -179,7 +180,8 @@ public class MotionEventSynthesizerImpl implements MotionEventSynthesizer {
         if (MotionEventAction.HOVER_EXIT == action) androidAction = MotionEvent.ACTION_HOVER_EXIT;
         if (MotionEventAction.HOVER_MOVE == action) androidAction = MotionEvent.ACTION_HOVER_MOVE;
         MotionEvent event = MotionEvent.obtain(mDownTimeInMs, timeInMs, androidAction, pointerCount,
-                mPointerProperties, mPointerCoords, 0, 0, 1, 1, 0, 0, 0, 0);
+                mPointerProperties, mPointerCoords, 0, 0, 1, 1, 0, 0,
+                InputDevice.SOURCE_CLASS_POINTER, 0);
         mTarget.dispatchGenericMotionEvent(event);
         event.recycle();
     }