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 177 matching lines @@
       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_mainThreadScrollingReasons(0) {
+      m_mainThreadScrollingReasons(0),
+      m_mainThreadScrollingReasonsCounter(
+          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 4569 matching lines @@
 MainThreadScrollingReasons FrameView::mainThreadScrollingReasonsPerFrame()
     const {
   MainThreadScrollingReasons reasons =
       static_cast<MainThreadScrollingReasons>(0);
 
   if (shouldThrottleRendering())
     return reasons;
 
   if (hasBackgroundAttachmentFixedObjects())
     reasons |= MainThreadScrollingReason::kHasBackgroundAttachmentFixedObjects;
+
+  reasons |= getStyleRelatedMainThreadScrollingReasons();
+
   ScrollingReasons scrollingReasons = getScrollingReasons();
   const bool mayBeScrolledByInput = (scrollingReasons == Scrollable);
   const bool mayBeScrolledByScript =
       mayBeScrolledByInput ||
       (scrollingReasons == NotScrollableExplicitlyDisabled);
 
   // TODO(awoloszyn) Currently crbug.com/304810 will let certain
   // overflow:hidden elements scroll on the compositor thread, so we should
   // not let this move there path as an optimization, when we have
   // slow-repaint elements.
@@ skipping 44 matching lines @@
             .c_str());
     return result;
   }
 
   String result(MainThreadScrollingReason::mainThreadScrollingReasonsAsText(
                     m_mainThreadScrollingReasons)
                     .c_str());
   return result;
 }
 
+void FrameView::adjustStyleRelatedMainThreadScrollingReasons(
+    const uint32_t reason,
+    bool increase) {
+  int index = MainThreadScrollingReason::getReasonIndex(reason);
+  DCHECK_GE(index, 0);
+  m_mainThreadScrollingReasonsCounter[index] += increase ? 1 : -1;
+  DCHECK_GE(m_mainThreadScrollingReasonsCounter[index], 0);
+}
+
+MainThreadScrollingReasons
+FrameView::getStyleRelatedMainThreadScrollingReasons() const {
+  MainThreadScrollingReasons reasons =
+      static_cast<MainThreadScrollingReasons>(0);
+  for (uint32_t reason = 1;
+       reason < MainThreadScrollingReason::kMainThreadScrollingReasonCount;
+       ++reason) {
+    if (m_mainThreadScrollingReasonsCounter[reason] > 0) {
+      reasons |= 1 << (reason - 1);
+    }
+  }
+  return reasons;
+}
+
 }  // namespace blink