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}

5 files changed, 11 insertions, 43 deletions

diff --git a/third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.cpp b/third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.cpp
index e7ca148..26f74ec 100644
--- a/third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.cpp
+++ b/third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.cpp
@@ -56,13 +56,11 @@
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/ScriptForbiddenScope.h"
 #include "platform/TraceEvent.h"
-#include "platform/geometry/FloatRect.h"
 #include "platform/graphics/CompositorMutableProperties.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/graphics/paint/CullRect.h"
 #include "platform/graphics/paint/DrawingRecorder.h"
 #include "platform/graphics/paint/PaintController.h"
-#include "platform/graphics/paint/SkPictureBuilder.h"
 #include "platform/graphics/paint/TransformDisplayItem.h"
 
 namespace blink {
@@ -793,8 +791,11 @@ bool PaintLayerCompositor::needsContentsCompositingLayer(const PaintLayer* layer
     return layer->stackingNode()->hasNegativeZOrderList();
 }
 
-static void paintScrollbar(const GraphicsLayer* graphicsLayer, const Scrollbar* scrollbar, GraphicsContext& context, const IntRect& clip)
+static void paintScrollbar(const Scrollbar* scrollbar, GraphicsContext& context, const IntRect& clip)
 {
+    if (!scrollbar)
+        return;
+
     // Frame scrollbars are painted in the space of the containing frame, not the local space of the scrollbar.
     const IntPoint& paintOffset = scrollbar->frameRect().location();
     IntRect transformedClip = clip;
@@ -803,6 +804,7 @@ static void paintScrollbar(const GraphicsLayer* graphicsLayer, const Scrollbar*
     AffineTransform translation;
     translation.translate(-paintOffset.x(), -paintOffset.y());
     TransformRecorder transformRecorder(context, *scrollbar, translation);
+
     scrollbar->paint(context, CullRect(transformedClip));
 }
 
@@ -813,37 +815,12 @@ IntRect PaintLayerCompositor::computeInterestRect(const GraphicsLayer* graphicsL
 
 void PaintLayerCompositor::paintContents(const GraphicsLayer* graphicsLayer, GraphicsContext& context, GraphicsLayerPaintingPhase, const IntRect& interestRect) const
 {
-    const Scrollbar* scrollbar = graphicsLayerToScrollbar(graphicsLayer);
-    if (!scrollbar && graphicsLayer != layerForScrollCorner())
-        return;
-
-    if (DrawingRecorder::useCachedDrawingIfPossible(context, *graphicsLayer, DisplayItem::ScrollbarCompositedScrollbar))
-        return;
-
-    FloatRect layerBounds(FloatPoint(), graphicsLayer->size());
-    SkPictureBuilder pictureBuilder(layerBounds, nullptr, &context);
-
-    if (scrollbar)
-        paintScrollbar(graphicsLayer, scrollbar, pictureBuilder.context(), interestRect);
-    else
-        FramePainter(*m_layoutView.frameView()).paintScrollCorner(pictureBuilder.context(), interestRect);
-
-    // Replay the painted scrollbar content with the GraphicsLayer backing as the DisplayItemClient
-    // in order for the resulting DrawingDisplayItem to produce the correct visualRect (i.e., the
-    // bounds of the involved GraphicsLayer).
-    DrawingRecorder drawingRecorder(context, *graphicsLayer, DisplayItem::ScrollbarCompositedScrollbar, layerBounds);
-    pictureBuilder.endRecording()->playback(context.canvas());
-}
-
-Scrollbar* PaintLayerCompositor::graphicsLayerToScrollbar(const GraphicsLayer* graphicsLayer) const
-{
-    if (graphicsLayer == layerForHorizontalScrollbar()) {
-        return m_layoutView.frameView()->horizontalScrollbar();
-    }
-    if (graphicsLayer == layerForVerticalScrollbar()) {
-        return m_layoutView.frameView()->verticalScrollbar();
-    }
-    return nullptr;
+    if (graphicsLayer == layerForHorizontalScrollbar())
+        paintScrollbar(m_layoutView.frameView()->horizontalScrollbar(), context, interestRect);
+    else if (graphicsLayer == layerForVerticalScrollbar())
+        paintScrollbar(m_layoutView.frameView()->verticalScrollbar(), context, interestRect);
+    else if (graphicsLayer == layerForScrollCorner())
+        FramePainter(*m_layoutView.frameView()).paintScrollCorner(context, interestRect);
 }
 
 bool PaintLayerCompositor::supportsFixedRootBackgroundCompositing() const
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;
 
diff --git a/third_party/WebKit/Source/core/paint/PaintInvalidationCapableScrollableArea.cpp b/third_party/WebKit/Source/core/paint/PaintInvalidationCapableScrollableArea.cpp
index 5175913..b063c64 100644
--- a/third_party/WebKit/Source/core/paint/PaintInvalidationCapableScrollableArea.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintInvalidationCapableScrollableArea.cpp
@@ -66,8 +66,6 @@ static void invalidatePaintOfScrollbarIfNeeded(Scrollbar* scrollbar, GraphicsLay
         // of the scrollbar on the box's paint invalidation container to ensure newly expanded/shrunk areas
         // of the box to be invalidated.
         needsPaintInvalidation = false;
-
-        graphicsLayer->invalidateDisplayItemClient(*graphicsLayer, PaintInvalidationScroll);
     }
 
     // Invalidate the box's display item client if the box's padding box size is affected by change of the
diff --git a/third_party/WebKit/Source/platform/graphics/paint/DisplayItem.cpp b/third_party/WebKit/Source/platform/graphics/paint/DisplayItem.cpp
index c5c3db9..1e9b880 100644
--- a/third_party/WebKit/Source/platform/graphics/paint/DisplayItem.cpp
+++ b/third_party/WebKit/Source/platform/graphics/paint/DisplayItem.cpp
@@ -101,7 +101,6 @@ static WTF::String specialDrawingTypeAsDebugString(DisplayItem::Type type)
         DEBUG_STRING_CASE(ScrollbarThumb);
         DEBUG_STRING_CASE(ScrollbarTickmarks);
         DEBUG_STRING_CASE(ScrollbarTrackBackground);
-        DEBUG_STRING_CASE(ScrollbarCompositedScrollbar);
         DEBUG_STRING_CASE(SelectionTint);
         DEBUG_STRING_CASE(TableCellBackgroundFromColumnGroup);
         DEBUG_STRING_CASE(TableCellBackgroundFromColumn);
diff --git a/third_party/WebKit/Source/platform/graphics/paint/DisplayItem.h b/third_party/WebKit/Source/platform/graphics/paint/DisplayItem.h
index 2f402fb..2ae4995 100644
--- a/third_party/WebKit/Source/platform/graphics/paint/DisplayItem.h
+++ b/third_party/WebKit/Source/platform/graphics/paint/DisplayItem.h
@@ -92,7 +92,6 @@ public:
         ScrollbarThumb,
         ScrollbarTickmarks,
         ScrollbarTrackBackground,
-        ScrollbarCompositedScrollbar,
         SelectionTint,
         TableCellBackgroundFromColumnGroup,
         TableCellBackgroundFromColumn,