Move logic of recording main thread scrolling reasons from cc to blink::ScrollManager

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp

Index: third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
index 638fee9b21f556ec1fbc90022b7def3c8a49bb28..3eda3a9d35244eb7b1a9b8b71c857b8e5156560d 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
@@ -114,7 +114,7 @@ PaintLayerScrollableArea::PaintLayerScrollableArea(PaintLayer& layer)
       scroll_corner_(nullptr),
       resizer_(nullptr),
       scroll_anchor_(this),
-      reasons_(0)
+      non_composited_main_thread_scrolling_reasons_(0)
 #if DCHECK_IS_ON()
       ,
       has_been_disposed_(false)
@@ -152,7 +152,7 @@ void PaintLayerScrollableArea::Dispose() {
     }
   }
 
-  RemoveStyleRelatedMainThreadScrollingReasons();
+  non_composited_main_thread_scrolling_reasons_ = 0;
 
   if (ScrollingCoordinator* scrolling_coordinator = GetScrollingCoordinator())
     scrolling_coordinator->WillDestroyScrollableArea(this);
@@ -1796,6 +1796,7 @@ bool PaintLayerScrollableArea::ShouldScrollOnMainThread() const {
 bool PaintLayerScrollableArea::ComputeNeedsCompositedScrolling(
     const LCDTextMode mode,
     const PaintLayer* layer) {
+  non_composited_main_thread_scrolling_reasons_ = 0;
   if (!layer->ScrollsOverflow())
     return false;
 
@@ -1810,14 +1811,14 @@ bool PaintLayerScrollableArea::ComputeNeedsCompositedScrolling(
     return false;
 
   bool needs_composited_scrolling = true;
-  uint32_t main_thread_scrolling_reasons = 0;
 
   // TODO(flackr): Allow integer transforms as long as all of the ancestor
   // transforms are also integer.
   bool background_supports_lcd_text =
       RuntimeEnabledFeatures::compositeOpaqueScrollersEnabled() &&
       layer->GetLayoutObject().Style()->IsStackingContext() &&
-      layer->GetBackgroundPaintLocation(&main_thread_scrolling_reasons) &
+      layer->GetBackgroundPaintLocation(
+          &non_composited_main_thread_scrolling_reasons_) &
           kBackgroundPaintInScrollingContents &&
       layer->BackgroundIsKnownToBeOpaqueInRect(
           ToLayoutBox(layer->GetLayoutObject()).PaddingBoxRect()) &&
@@ -1827,16 +1828,16 @@ bool PaintLayerScrollableArea::ComputeNeedsCompositedScrolling(
       !layer->Compositor()->PreferCompositingToLCDTextEnabled() &&
       !background_supports_lcd_text) {
     if (layer->CompositesWithOpacity()) {
-      main_thread_scrolling_reasons |=
+      non_composited_main_thread_scrolling_reasons_ |=
           MainThreadScrollingReason::kHasOpacityAndLCDText;
     }
     if (layer->CompositesWithTransform()) {
-      main_thread_scrolling_reasons |=
+      non_composited_main_thread_scrolling_reasons_ |=
           MainThreadScrollingReason::kHasTransformAndLCDText;
     }
     if (!layer->BackgroundIsKnownToBeOpaqueInRect(
             ToLayoutBox(layer->GetLayoutObject()).PaddingBoxRect())) {
-      main_thread_scrolling_reasons |=
+      non_composited_main_thread_scrolling_reasons_ |=
           MainThreadScrollingReason::kBackgroundNotOpaqueInRectAndLCDText;
     }
 
@@ -1848,68 +1849,24 @@ bool PaintLayerScrollableArea::ComputeNeedsCompositedScrolling(
   // behind dashed borders). Resolve this case, or not, and update this check
   // with the results.
   if (layer->GetLayoutObject().Style()->HasBorderRadius()) {
-    main_thread_scrolling_reasons |=
+    non_composited_main_thread_scrolling_reasons_ |=
         MainThreadScrollingReason::kHasBorderRadius;
     needs_composited_scrolling = false;
   }
   if (layer->GetLayoutObject().HasClip() ||
       layer->HasDescendantWithClipPath() || layer->HasAncestorWithClipPath()) {
-    main_thread_scrolling_reasons |=
+    non_composited_main_thread_scrolling_reasons_ |=
         MainThreadScrollingReason::kHasClipRelatedProperty;
     needs_composited_scrolling = false;
   }
 
-  if (main_thread_scrolling_reasons) {
-    AddStyleRelatedMainThreadScrollingReasons(main_thread_scrolling_reasons);
-  }
-
+  DCHECK(!(non_composited_main_thread_scrolling_reasons_ &
+           ~MainThreadScrollingReason::kNonCompositedReasons));
   return needs_composited_scrolling;
 }
 
-void PaintLayerScrollableArea::AddStyleRelatedMainThreadScrollingReasons(
-    const uint32_t reasons) {
-  LocalFrame* frame = Box().GetFrame();
-  if (!frame)
-    return;
-  FrameView* frame_view = frame->View();
-  if (!frame_view)
-    return;
-
-  for (uint32_t reason = 1;
-       reason < 1 << MainThreadScrollingReason::kMainThreadScrollingReasonCount;
-       reason <<= 1) {
-    if (reasons & reason) {
-      frame_view->AdjustStyleRelatedMainThreadScrollingReasons(reason, true);
-      reasons_ |= reason;
-    }
-  }
-}
-
-void PaintLayerScrollableArea::RemoveStyleRelatedMainThreadScrollingReasons() {
-  LocalFrame* frame = Box().GetFrame();
-  if (!frame)
-    return;
-  FrameView* frame_view = frame->View();
-  if (!frame_view)
-    return;
-
-  // Decrease the number of layers that have any main thread
-  // scrolling reasons stored in FrameView
-  for (uint32_t i = 0;
-       i < MainThreadScrollingReason::kMainThreadScrollingReasonCount; ++i) {
-    uint32_t reason = 1 << i;
-    if (HasMainThreadScrollingReason(reason)) {
-      reasons_ &= ~reason;
-      frame_view->AdjustStyleRelatedMainThreadScrollingReasons(reason, false);
-    }
-  }
-}
-
 void PaintLayerScrollableArea::UpdateNeedsCompositedScrolling(
     LCDTextMode mode) {
-  // Clear all style related main thread scrolling reasons, if any,
-  // before calling computeNeedsCompositedScrolling
-  RemoveStyleRelatedMainThreadScrollingReasons();
   const bool needs_composited_scrolling =
       ComputeNeedsCompositedScrolling(mode, Layer());