[RootLayerScrolls] Update scroll dimensions before clamping

When an overflow:auto vertical scrollbar is removed from an RTL
LayoutView, then the call to ClampScrollOffsetAfterOverflowChange in
LayoutView::UpdateAfterLayout during the second layout pass (after
removing the scrollbar) will happen when the ScrollableArea's
overflow_rect_ needs updating.

BUG=711468
R=skobes@chromium.org,pdr@chromium.org,bokan@chromium.org

Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_root_layer_scrolls;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: I191a7142808851b266904b1916afc57b4b305940
Reviewed-on: https://chromium-review.googlesource.com/802179
Commit-Queue: Stefan Zager <szager@chromium.org>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521607}

third_party/WebKit/LayoutTests/FlagExpectations/root-layer-scrolls

@@ -3,7 +3,6 @@ crbug.com/417782 compositing/layer-creation/iframe-background-attachment-fixed.h
 crbug.com/417782 compositing/squashing/squash-above-fixed-1.html [ Failure ]
 crbug.com/417782 compositing/squashing/squash-above-fixed-3.html [ Failure ]
 crbug.com/417782 compositing/visibility/visibility-image-layers-dynamic.html [ Failure ]
-crbug.com/417782 [ Linux Mac ] fast/dom/horizontal-scrollbar-when-dir-change.html [ Failure ]
 crbug.com/417782 fast/dom/rtl-scroll-to-leftmost-and-resize.html [ Failure ]
 crbug.com/417782 fast/dom/scroll-reveal-left-overflow.html [ Failure ]
 crbug.com/417782 fast/dom/scroll-reveal-top-overflow.html [ Failure ]

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

@@ -749,11 +749,6 @@ void LocalFrameView::SetLayoutOverflowSize(const IntSize& size) {
     return;
 
   page->GetChromeClient().ContentsSizeChanged(frame_.Get(), size);
-
-  // Ensure the scrollToFragmentAnchor is called before
-  // restoreScrollPositionAndViewState when reload
-  ScrollToFragmentAnchor();
-  GetFrame().Loader().RestoreScrollPositionAndViewState();
 }
 
 void LocalFrameView::AdjustViewSize() {
@@ -2627,7 +2622,10 @@ void LocalFrameView::PerformPostLayoutTasks() {
     scrolling_coordinator->NotifyGeometryChanged(this);
   }
 
+  // If we're restoring a scroll position from history, that takes precedence
+  // over scrolling to the anchor in the URL.
   ScrollToFragmentAnchor();
+  GetFrame().Loader().RestoreScrollPositionAndViewState();
   SendResizeEventIfNeeded();
 }
 

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

@@ -954,6 +954,7 @@ void PaintLayerScrollableArea::ClampScrollOffsetAfterOverflowChange() {
     return;
   }
 
+  UpdateScrollDimensions();
   if (ScrollOriginChanged())
     SetScrollOffsetUnconditionally(ClampScrollOffset(GetScrollOffset()));
   else