Add more specific metrics for main thread scrolling reasons

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

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 176 matching lines @@
       m_hiddenForThrottling(false),
       m_subtreeThrottled(false),
       m_lifecycleUpdatesThrottled(false),
       m_needsPaintPropertyUpdate(true),
       m_currentUpdateLifecyclePhasesTargetState(
           DocumentLifecycle::Uninitialized),
       m_scrollAnchor(this),
       m_scrollbarManager(*this),
       m_needsScrollbarsUpdate(false),
       m_suppressAdjustViewSize(false),
-      m_allowsLayoutInvalidationAfterLayoutClean(true) {
+      m_allowsLayoutInvalidationAfterLayoutClean(true),
+      m_mainThreadScrollingReasonLayoutCounter(
+          MainThreadScrollingReason::kMainThreadScrollingReasonCount,
+          0) {
   init();
 }
 
 FrameView* FrameView::create(LocalFrame& frame) {
   FrameView* view = new FrameView(frame);
   view->show();
   return view;
 }
 
 FrameView* FrameView::create(LocalFrame& frame, const IntSize& initialSize) {
@@ skipping 4460 matching lines @@
 int FrameView::initialViewportWidth() const {
   DCHECK(m_frame->isMainFrame());
   return m_initialViewportSize.width();
 }
 
 int FrameView::initialViewportHeight() const {
   DCHECK(m_frame->isMainFrame());
   return m_initialViewportSize.height();
 }
 
+void FrameView::adjustMainThreadReasonsDueToLayoutObject(uint32_t reason,
+                                                         bool increase) {
+  m_mainThreadScrollingReasonLayoutCounter[reasonIndex(reason)] +=

[bokan, 2016/12/13 14:38:56]

This should never be negative, right? If so, please DCHECK that it isn't.

[yigu, 2016/12/13 20:54:10]

Done.

+      increase ? 1 : -1;
+}
+
+MainThreadScrollingReasons
+FrameView::checkMainThreadScrollingReasonDueToLayoutObject() {
+  MainThreadScrollingReasons reasons =
+      static_cast<MainThreadScrollingReasons>(0);
+  for (uint32_t reason = 1;
+       reason < MainThreadScrollingReason::kMainThreadScrollingReasonCount;
+       ++reason) {
+    if (m_mainThreadScrollingReasonLayoutCounter[reason] > 0) {
+      reasons |= 1 << (reason - 1);
+    }
+  }
+  return reasons;
+}
+
 }  // namespace blink