Update PaintLayer size during layout, not after.

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

Index: third_party/WebKit/Source/core/paint/PaintLayer.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayer.cpp b/third_party/WebKit/Source/core/paint/PaintLayer.cpp
index de41d0c41ab71484546034640bccb6b362461183..b01234185f8299e4612b0955d5253e096afce680 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayer.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayer.cpp
@@ -786,17 +786,13 @@ void PaintLayer::Update3DTransformedDescendantStatus() {
 }
 
 void PaintLayer::UpdateLayerPosition() {
+  // LayoutBoxes will call UpdateSizeAndScrollingAfterLayout() from
+  // LayoutBox::UpdateAfterLayout, but LayoutInlines will still need to update
+  // their size.
+  if (GetLayoutObject().IsInline() && GetLayoutObject().IsLayoutInline())
+    UpdateSizeAndScrollingAfterLayout();
   LayoutPoint local_point;
-
-  bool did_resize = false;
-  if (GetLayoutObject().IsInline() && GetLayoutObject().IsLayoutInline()) {
-    LayoutInline& inline_flow = ToLayoutInline(GetLayoutObject());
-    IntRect line_box = EnclosingIntRect(inline_flow.LinesBoundingBox());
-    size_ = line_box.Size();
-  } else if (LayoutBox* box = GetLayoutBox()) {
-    IntSize new_size = PixelSnappedIntSize(box->Size(), box->Location());
-    did_resize = new_size != size_;
-    size_ = new_size;
+  if (LayoutBox* box = GetLayoutBox()) {
     local_point.MoveBy(box->PhysicalLocation());
   }
 
@@ -847,17 +843,32 @@ void PaintLayer::UpdateLayerPosition() {
 
   location_ = local_point;
 
-  if (scrollable_area_ && did_resize)
-    scrollable_area_->VisibleSizeChanged();
-
 #if DCHECK_IS_ON()
   needs_position_update_ = false;
 #endif
 }
 
-void PaintLayer::UpdateScrollingAfterLayout() {
-  if (GetLayoutObject().HasOverflowClip())
+void PaintLayer::UpdateSizeAndScrollingAfterLayout() {
+  bool did_resize = false;
+  if (IsRootLayer() && RuntimeEnabledFeatures::rootLayerScrollingEnabled()) {
+    const IntSize new_size = GetLayoutObject().GetDocument().View()->Size();
+    did_resize = new_size != size_;
+    size_ = new_size;
+  } else if (GetLayoutObject().IsInline() &&
+             GetLayoutObject().IsLayoutInline()) {
+    LayoutInline& inline_flow = ToLayoutInline(GetLayoutObject());
+    IntRect line_box = EnclosingIntRect(inline_flow.LinesBoundingBox());
+    size_ = line_box.Size();
+  } else if (LayoutBox* box = GetLayoutBox()) {
+    IntSize new_size = PixelSnappedIntSize(box->Size(), box->Location());
+    did_resize = new_size != size_;
+    size_ = new_size;
+  }
+  if (GetLayoutObject().HasOverflowClip()) {
     scrollable_area_->UpdateAfterLayout();
+    if (did_resize)
+      scrollable_area_->VisibleSizeChanged();
+  }
 }
 
 TransformationMatrix PaintLayer::PerspectiveTransform() const {