Add UMA stats for pinch-zoom behavior on Android

third_party/WebKit/Source/web/WebViewImpl.cpp

 /*
  * Copyright (C) 2011, 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 2054 matching lines @@
     // on the page. There is a single input event, GestureTap, which can both
     // be the first event after page load, and cause a form submission. In that
     // case, the form submission happens before the autofill client is told
     // to unblock the password values, and so the password values are not
     // submitted. To avoid that, GestureTap is handled explicitly:
     if (inputEvent.type == WebInputEvent::GestureTap && autofillClient) {
         m_userGestureObserved = true;
         autofillClient->firstUserGestureObserved();
     }
 
+    page()->frameHost().visualViewport().startTrackingPinchStats();

[Yoav Weiss, 2015/09/25 08:46:59]

Would that mean that we start tracking pinch zoom regardless of the input event
type?

[bokan, 2015/09/25 17:01:48]

Yes, I use it more as a signal that this is something the user can see and
interact with. Though on Android I think that's pretty much just touches...

+
     TRACE_EVENT1("input", "WebViewImpl::handleInputEvent", "type", inputTypeToName(inputEvent.type).ascii());
     // If we've started a drag and drop operation, ignore input events until
     // we're done.
     if (m_doingDragAndDrop)
         return true;
 
     if (m_devToolsEmulator->handleInputEvent(inputEvent))
         return true;
 
     if (InspectorOverlay* overlay = inspectorOverlay()) {
@@ skipping 2135 matching lines @@
     FrameView* frameView = mainFrameImpl()->frameView();
     if (!frameView)
         return;
 
     topControls().setShownRatio(topControls().shownRatio() + topControlsShownRatioDelta);
 
     FloatPoint visualViewportOffset = page()->frameHost().visualViewport().visibleRect().location();
     visualViewportOffset.move(visualViewportDelta.width, visualViewportDelta.height);
     setPageScaleFactorAndLocation(pageScaleFactor() * pageScaleDelta, visualViewportOffset);
 
-    if (pageScaleDelta != 1)
+    if (pageScaleDelta != 1) {

[Yoav Weiss, 2015/09/25 08:46:59]

What's the pageScaleDelta value in non-mobile zoom-out scenarios? I'd assume
it's lower than 1 and would be counted as a scale change.

[bokan, 2015/09/25 17:01:48]

This is the delta coming from the compositor. As such, it's only the *change* in
page scale that occured on the compositor that Blink doesn't know about yet. The
only changes from the compositor are due to pinch-zoom, double-tap to zoom
animations, and zoom-to-legible text editing. The initial page scale that gets
set on non-mobile pages is done from the Blink main thread and sent to the
compositor.

         m_doubleTapZoomPending = false;
+        page()->frameHost().visualViewport().userDidChangeScale();
+    }
 
     m_elasticOverscroll += elasticOverscrollDelta;
     frameView->didUpdateElasticOverscroll();
 
     ScrollableArea* layoutViewport = frameView->layoutViewportScrollableArea();
 
     DoublePoint layoutViewportPosition = layoutViewport->scrollPositionDouble()
         + DoubleSize(layoutViewportDelta.width, layoutViewportDelta.height);
 
     if (layoutViewport->scrollPositionDouble() != layoutViewportPosition) {
@@ skipping 187 matching lines @@
     if (m_pageColorOverlay)
         m_pageColorOverlay->update();
     if (InspectorOverlay* overlay = inspectorOverlay()) {
         PageOverlay* inspectorPageOverlay = overlay->pageOverlay();
         if (inspectorPageOverlay)
             inspectorPageOverlay->update();
     }
 }
 
 } // namespace blink