Experiment with emulating mouse hover with touch hover capable devices

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

Index: content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
diff --git a/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java b/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
index 20c24c2d600a24530ff17f1fba9dbee275a23425..8a6ed8a19e76029ebb111ca2fdc8a9e7ba3d4e76 100644
--- a/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
+++ b/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
@@ -1550,6 +1550,12 @@ public class ContentViewCore
      */
     public boolean onHoverEvent(MotionEvent event) {
         TraceEvent.begin("onHoverEvent");
+        // Dispatch a mouseover event when the touch hover switch is on and the event is
+        // a finger hover.

[Rick Byers, 2014/11/13 19:32:15]

Please add a comment like:
TODO(lanwei) Remove this switch once experimentation is complete -
crbug.com/418188

We can leave the bug open until we either decide to ship this enabled by
default, or abort the experiment (too often we forget to do the final cleanup of
removing code for flags which are no longer experimental)...

[lanwei, 2014/12/01 15:25:19]

Done.

+        if (!CommandLine.getInstance().hasSwitch(ContentSwitches.ENABLE_TOUCH_HOVER)
+                && event.getToolType(0) == MotionEvent.TOOL_TYPE_FINGER
+                && event.getSource() == InputDevice.SOURCE_TOUCHSCREEN)
+            return true;

[jdduke (slow), 2014/11/13 19:38:44]

So the SPen hover events always indicate that they're from a finger?  

Also, we should cache the command line check (let's have a static method with a
static Boolean that's initialized just once (when null)).

static boolean touchHoverEventsEnabled() {
  if (sTouchHoverEventsEnabled == null) {
     ...
   }
   return sTouchHoverEventsEnabled;
}

Hmm, now I'm wondering if the query should go in SPenSupport.java? That might
also let us restrict the case when we filter the hover events (isSPenSupported()
will be true).

[jdduke (slow), 2014/11/13 19:47:40]

Nevermind, I thought the airview feature was SPen-specific but it's not.

[lanwei, 2014/12/01 15:25:19]

Done.

         MotionEvent offset = createOffsetMotionEvent(event);
         try {
             if (mBrowserAccessibilityManager != null) {