Revert of Make GraphicsLayer the DisplayItemClient for scrollbars composited via PaintLayerCompositor. (patchset #6 id:100001 of https://codereview.chromium.org/1825193002/ )

Reason for revert:
Speculative revert: this may cause crash for rasterize_and_record_micro benchmark.

BUG=597391

Original issue's description:
> Make GraphicsLayer the DisplayItemClient for scrollbars composited via PaintLayerCompositor.
>
> Currently, the DisplayItemClient is LayoutScrollbarPart. This has two
> problems: the mapping between the LayoutScrollbarPart and its backing
> is hard to reverse-engineer given the way the scrollbar code is set
> up (LayoutScrollbarPart vs Scrollbar vs ScrollableArea), and the
> fact that LayoutScrollbarPart can be painted in both non-composited
> and composited modes. This distinction is important for computation
> of correct visual rects.
>
> This can be cleaned up by replaying the painted scrollbar content
> with the GraphicsLayer backing as the DisplayItemClient, which
> has the correct visualRect() (i.e. bounds of GraphicsLayer).
>
> BUG=529938
>
> Committed: https://crrev.com/8460ef8fc6125185abc1486eb61b0ca7fc9298ad
> Cr-Commit-Position: refs/heads/master@{#382778}

TBR=chrishtr@chromium.org,wkorman@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=529938

Review URL: https://codereview.chromium.org/1839533002

Cr-Commit-Position: refs/heads/master@{#383451}

1 files changed, 0 insertions, 5 deletions

diff --git a/third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.h b/third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.h
index d71d791..c4c46d5 100644
--- a/third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.h
+++ b/third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.h
@@ -39,7 +39,6 @@ class GraphicsLayer;
 class IntPoint;
 class Page;
 class LayoutPart;
-class Scrollbar;
 class ScrollingCoordinator;
 
 enum CompositingUpdateType {
@@ -211,10 +210,6 @@ private:
 
     void applyOverlayFullscreenVideoAdjustmentIfNeeded();
 
-    // Checks the given graphics layer against the compositor's horizontal and vertical scrollbar
-    // graphics layers, returning the associated Scrollbar instance if any, else nullptr.
-    Scrollbar* graphicsLayerToScrollbar(const GraphicsLayer*) const;
-
     LayoutView& m_layoutView;
     OwnPtr<GraphicsLayer> m_rootContentLayer;