[Android] Fix a bug where the suggestion list can't scroll

After we placed omnibox suggestion list as a child of
CompositorViewHolder, it no longer is able to scroll.

The investigation of this regression gave interesting result: if an
ACTION_MOVE is dispatched to a ListView or a ScrollView and the
ViewGroup intercepts it, the framework will generate an ACTION_CANCEL to
the ViewGroup's children. The behavior, however, will steal this cancel
event and send to the ViewGroup again, causing scroll to fail. Thus we
should specifically not catch ACTION_CANCEL in behavior.

BUG=648136

Review-Url: https://codereview.chromium.org/2526673004
Cr-Commit-Position: refs/heads/master@{#434761}

chrome/android/java/src/org/chromium/chrome/browser/compositor/CompositorViewHolderBehavior.java

@@ -40,7 +40,13 @@ public class CompositorViewHolderBehavior extends Behavior<View> {
 
     @Override
     public boolean onTouchEvent(CoordinatorLayout parent, View child, MotionEvent ev) {
-        if (!mShouldIntercept) return false;
+        // If an ACTION_MOVE is dispatched to a ListView or a ScrollView and the ViewGroup
+        // intercepts it, the framework will generate an ACTION_CANCEL to the ViewGroup's children.
+        // This class, however, will steal this cancel event and send to the ViewGroup again,
+        // causing scroll to fail. Thus we should specifically not catch ACTION_CANCEL in behavior.
+        // In theory, stopping ACTION_CANCEL will cause problem when CompositorViewHolder scrolls.
+        // Yet currently CompositorViewHolder does not scroll.
+        if (!mShouldIntercept || ev.getActionMasked() == MotionEvent.ACTION_CANCEL) return false;
         ev.offsetLocation(-child.getX(), -child.getY());
         child.dispatchTouchEvent(ev);
         return true;