Add metric to know how user use scrollbar

third_party/WebKit/Source/platform/scroll/Scrollbar.cpp

 /*
  * Copyright (C) 2004, 2006, 2008 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "platform/scroll/Scrollbar.h"
 
-#include <algorithm>
+#include "platform/Histogram.h"
 #include "platform/HostWindow.h"
 #include "platform/PlatformMouseEvent.h"
 #include "platform/geometry/FloatRect.h"
 #include "platform/graphics/paint/CullRect.h"
 #include "platform/scroll/ScrollAnimatorBase.h"
 #include "platform/scroll/ScrollableArea.h"
 #include "platform/scroll/ScrollbarTheme.h"
 #include "public/platform/WebGestureEvent.h"
 
 namespace blink {
@@ skipping 271 matching lines @@
   m_hoveredPart = part;
 }
 
 void Scrollbar::setPressedPart(ScrollbarPart part) {
   if (m_pressedPart != NoPart
       // When we no longer have a pressed part, we can start drawing a hovered
       // state on the hovered part.
       || m_hoveredPart != NoPart)
     setNeedsPaintInvalidation(
         static_cast<ScrollbarPart>(m_pressedPart | m_hoveredPart | part));
+
+  sendScrollbarUseUMA(part);
   m_pressedPart = part;
 }
 
+void Scrollbar::sendScrollbarUseUMA(ScrollbarPart part) {
+  DCHECK(root());
+
+  ScrollbarUseUMA scrollbarUseUMA = IgnorePart;
+  switch (part) {
+    case BackButtonStartPart:
+    case ForwardButtonStartPart:
+    case BackButtonEndPart:
+    case ForwardButtonEndPart:
+      scrollbarUseUMA =
+          (orientation() == VerticalScrollbar ? VerticalScrollbarButton
+                                              : HorizontalScrollbarButton);
+      break;
+    case ThumbPart:
+      scrollbarUseUMA =
+          (orientation() == VerticalScrollbar ? VerticalScrollbarThumb
+                                              : HorizontalScrollbarThumb);
+      break;
+    case BackTrackPart:
+    case ForwardTrackPart:
+      scrollbarUseUMA =
+          (orientation() == VerticalScrollbar ? VerticalScrollbarTrack
+                                              : HorizontalScrollbarTrack);
+      break;
+    default:
+      scrollbarUseUMA = IgnorePart;
+  }
+
+  if (scrollbarUseUMA != IgnorePart &&
+      root()->shouldSendScrollbarUseUMA(scrollbarUseUMA)) {
+    DEFINE_STATIC_LOCAL(EnumerationHistogram, scrollbarUseHistogram,
+                        ("Scrollbar.ScrollbarUse", ScrollbarUseUMAMax));
+    scrollbarUseHistogram.count(static_cast<ScrollbarUseUMA>(part));
+  }
+}
+
 bool Scrollbar::gestureEvent(const WebGestureEvent& evt,
                              bool* shouldUpdateCapture) {
   DCHECK(shouldUpdateCapture);
   switch (evt.type()) {
     case WebInputEvent::GestureTapDown: {
       IntPoint position = flooredIntPoint(evt.positionInRootFrame());
       setPressedPart(theme().hitTest(*this, position));
       m_pressedPos = orientation() == HorizontalScrollbar
                          ? convertFromRootFrame(position).x()
                          : convertFromRootFrame(position).y();
@@ skipping 296 matching lines @@
     invalidParts = AllParts;
   if (invalidParts & ~ThumbPart)
     m_trackNeedsRepaint = true;
   if (invalidParts & ThumbPart)
     m_thumbNeedsRepaint = true;
   if (m_scrollableArea)
     m_scrollableArea->setScrollbarNeedsPaintInvalidation(orientation());
 }
 
 }  // namespace blink