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 a6c4b4440b2bc3c701e2f9beaf71d61a293a8e20..d819b98ed158faa627929666a94774e94fd9e8ae 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
@@ -153,7 +153,7 @@ void PaintLayerScrollableArea::dispose() {
     }
   }
 
-  removeStyleRelatedMainThreadScrollingReasons();
+  resetStyleRelatedMainThreadScrollingReasons();
 
   if (ScrollingCoordinator* scrollingCoordinator = getScrollingCoordinator())
     scrollingCoordinator->willDestroyScrollableArea(this);
@@ -1788,14 +1788,13 @@ bool PaintLayerScrollableArea::computeNeedsCompositedScrolling(
     return false;
 
   bool needsCompositedScrolling = true;
-  uint32_t mainThreadScrollingReasons = 0;
 
   // TODO(flackr): Allow integer transforms as long as all of the ancestor
   // transforms are also integer.
   bool backgroundSupportsLCDText =
       RuntimeEnabledFeatures::compositeOpaqueScrollersEnabled() &&
       layer->layoutObject().style()->isStackingContext() &&
-      layer->backgroundPaintLocation(&mainThreadScrollingReasons) &
+      layer->backgroundPaintLocation(&m_reasons) &
           BackgroundPaintInScrollingContents &&
       layer->backgroundIsKnownToBeOpaqueInRect(
           toLayoutBox(layer->layoutObject()).paddingBoxRect()) &&
@@ -1805,16 +1804,14 @@ bool PaintLayerScrollableArea::computeNeedsCompositedScrolling(
       !layer->compositor()->preferCompositingToLCDTextEnabled() &&
       !backgroundSupportsLCDText) {
     if (layer->compositesWithOpacity()) {
-      mainThreadScrollingReasons |=
-          MainThreadScrollingReason::kHasOpacityAndLCDText;
+      m_reasons |= MainThreadScrollingReason::kHasOpacityAndLCDText;
     }
     if (layer->compositesWithTransform()) {
-      mainThreadScrollingReasons |=
-          MainThreadScrollingReason::kHasTransformAndLCDText;
+      m_reasons |= MainThreadScrollingReason::kHasTransformAndLCDText;
     }
     if (!layer->backgroundIsKnownToBeOpaqueInRect(
             toLayoutBox(layer->layoutObject()).paddingBoxRect())) {
-      mainThreadScrollingReasons |=
+      m_reasons |=
           MainThreadScrollingReason::kBackgroundNotOpaqueInRectAndLCDText;
     }
 
@@ -1826,67 +1823,23 @@ bool PaintLayerScrollableArea::computeNeedsCompositedScrolling(
   // behind dashed borders). Resolve this case, or not, and update this check
   // with the results.
   if (layer->layoutObject().style()->hasBorderRadius()) {
-    mainThreadScrollingReasons |= MainThreadScrollingReason::kHasBorderRadius;
+    m_reasons |= MainThreadScrollingReason::kHasBorderRadius;
     needsCompositedScrolling = false;
   }
   if (layer->layoutObject().hasClip() || layer->hasDescendantWithClipPath() ||
       layer->hasAncestorWithClipPath()) {
-    mainThreadScrollingReasons |=
-        MainThreadScrollingReason::kHasClipRelatedProperty;
+    m_reasons |= MainThreadScrollingReason::kHasClipRelatedProperty;
     needsCompositedScrolling = false;
   }
 
-  if (mainThreadScrollingReasons) {
-    addStyleRelatedMainThreadScrollingReasons(mainThreadScrollingReasons);
-  }
-
   return needsCompositedScrolling;
 }
 
-void PaintLayerScrollableArea::addStyleRelatedMainThreadScrollingReasons(
-    const uint32_t reasons) {
-  LocalFrame* frame = box().frame();
-  if (!frame)
-    return;
-  FrameView* frameView = frame->view();
-  if (!frameView)
-    return;
-
-  for (uint32_t reason = 1;
-       reason < 1 << MainThreadScrollingReason::kMainThreadScrollingReasonCount;
-       reason <<= 1) {
-    if (reasons & reason) {
-      frameView->adjustStyleRelatedMainThreadScrollingReasons(reason, true);
-      m_reasons |= reason;
-    }
-  }
-}
-
-void PaintLayerScrollableArea::removeStyleRelatedMainThreadScrollingReasons() {
-  LocalFrame* frame = box().frame();
-  if (!frame)
-    return;
-  FrameView* frameView = frame->view();
-  if (!frameView)
-    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)) {
-      m_reasons &= ~reason;
-      frameView->adjustStyleRelatedMainThreadScrollingReasons(reason, false);
-    }
-  }
-}
-
 void PaintLayerScrollableArea::updateNeedsCompositedScrolling(
     LCDTextMode mode) {
   // Clear all style related main thread scrolling reasons, if any,
   // before calling computeNeedsCompositedScrolling
-  removeStyleRelatedMainThreadScrollingReasons();
+  resetStyleRelatedMainThreadScrollingReasons();

[bokan, 2017/03/24 17:55:54]

We should reset the reasons inside computeNeedsCompositedScrolling.

[yigu, 2017/03/27 21:02:07]

Done.

   const bool needsCompositedScrolling =
       computeNeedsCompositedScrolling(mode, layer());