Add UMA stats for pinch-zoom behavior on Android

third_party/WebKit/Source/core/frame/VisualViewport.cpp

 /*
  * Copyright (C) 2013 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 53 matching lines @@
 using blink::FrameHost;
 using blink::GraphicsLayer;
 using blink::GraphicsLayerFactory;
 
 namespace blink {
 
 VisualViewport::VisualViewport(FrameHost& owner)
     : m_frameHost(&owner)
     , m_scale(1)
     , m_topControlsAdjustment(0)
+    , m_maxPageScale(-1)
+    , m_trackPinchZoomStatsForPage(false)
 {
     reset();
 }
 
 VisualViewport::~VisualViewport()
 {
+    sendUMAMetrics();
 }
 
 DEFINE_TRACE(VisualViewport)
 {
     visitor->trace(m_frameHost);
     ScrollableArea::trace(visitor);
 }
 
 void VisualViewport::setSize(const IntSize& size)
 {
@@ skipping 557 matching lines @@
     // FIXME: How to snap to pixels?
     return flooredIntPoint(FloatPoint(viewportToRootFrame(FloatPoint(pointInViewport))));
 }
 
 IntPoint VisualViewport::rootFrameToViewport(const IntPoint& pointInRootFrame) const
 {
     // FIXME: How to snap to pixels?
     return flooredIntPoint(FloatPoint(rootFrameToViewport(FloatPoint(pointInRootFrame))));
 }
 
+void VisualViewport::startTrackingPinchStats()
+{
+    if (!mainFrame())
+        return;
+
+    Document* document = mainFrame()->document();
+    if (!document)
+        return;
+
+    if (!document->url().protocolIsInHTTPFamily())
+        return;
+
+    m_trackPinchZoomStatsForPage = !shouldDisableDesktopWorkarounds();
+}
+
+void VisualViewport::userDidChangeScale()
+{
+    if (!m_trackPinchZoomStatsForPage)
+        return;
+
+    m_maxPageScale = std::max(m_maxPageScale, m_scale);
+}
+
+void VisualViewport::sendUMAMetrics()
+{
+    if (m_trackPinchZoomStatsForPage) {
+        bool didScale = m_maxPageScale > 0;
+
+        Platform::current()->histogramEnumeration("Viewport.DidScalePage", didScale ? 1 : 0, 2);
+
+        if (didScale) {
+            int zoomPercentage = floor(m_maxPageScale * 100);
+
+            // See the PageScaleFactor enumeration in histograms.xml for the bucket ranges.
+            int bucket = floor(zoomPercentage / 25.f);
+
+            Platform::current()->histogramEnumeration("Viewport.MaxPageScale", bucket, 21);
+        }
+    }
+
+    m_maxPageScale = -1;
+    m_trackPinchZoomStatsForPage = false;
+}
+
+bool VisualViewport::shouldDisableDesktopWorkarounds() const
+{
+    if (!mainFrame() || !mainFrame()->view())
+        return false;
+
+    if (!mainFrame()->settings()->viewportEnabled())
+        return false;
+
+    // A document is considered adapted to small screen UAs if one of these holds:
+    // 1. The author specified viewport has a constrained width that is equal to
+    //    the initial viewport width.
+    // 2. The author has disabled viewport zoom.
+    const PageScaleConstraints& constraints = frameHost().pageScaleConstraintsSet().pageDefinedConstraints();
+
+    return mainFrame()->view()->layoutSize().width() == m_size.width()
+        || (constraints.minimumScale == constraints.maximumScale && constraints.minimumScale != -1);
+}
+
 String VisualViewport::debugName(const GraphicsLayer* graphicsLayer)
 {
     String name;
     if (graphicsLayer == m_innerViewportContainerLayer.get()) {
         name = "Inner Viewport Container Layer";
     } else if (graphicsLayer == m_overscrollElasticityLayer.get()) {
         name =  "Overscroll Elasticity Layer";
     } else if (graphicsLayer == m_pageScaleLayer.get()) {
         name =  "Page Scale Layer";
     } else if (graphicsLayer == m_innerViewportScrollLayer.get()) {
         name =  "Inner Viewport Scroll Layer";
     } else if (graphicsLayer == m_overlayScrollbarHorizontal.get()) {
         name =  "Overlay Scrollbar Horizontal Layer";
     } else if (graphicsLayer == m_overlayScrollbarVertical.get()) {
         name =  "Overlay Scrollbar Vertical Layer";
     } else if (graphicsLayer == m_rootTransformLayer) {
         name =  "Root Transform Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace blink