Refactor DrawingRecorders to check for cached drawings earlier

Source/core/paint/BlockFlowPainter.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/paint/BlockFlowPainter.h"
 
 #include "core/layout/FloatingObjects.h"
 #include "core/layout/LayoutBlockFlow.h"
 #include "core/paint/ClipScope.h"
@@ skipping 35 matching lines @@
         }
     }
 }
 
 void BlockFlowPainter::paintSelection(const PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
     ASSERT(paintInfo.phase == PaintPhaseForeground);
     if (!m_layoutBlockFlow.shouldPaintSelectionGaps())
         return;
 
+    if (LayoutObjectDrawingRecorder::useCachedDrawingIfPossible(*paintInfo.context, m_layoutBlockFlow, DisplayItem::SelectionGap))
+        return;
+
     LayoutUnit lastTop = 0;
     LayoutUnit lastLeft = m_layoutBlockFlow.logicalLeftSelectionOffset(&m_layoutBlockFlow, lastTop);
     LayoutUnit lastRight = m_layoutBlockFlow.logicalRightSelectionOffset(&m_layoutBlockFlow, lastTop);
 
     LayoutRect bounds;
     if (RuntimeEnabledFeatures::slimmingPaintEnabled()) {
         bounds = m_layoutBlockFlow.visualOverflowRect();
         bounds.moveBy(paintOffset);
     }
     LayoutObjectDrawingRecorder recorder(*paintInfo.context, m_layoutBlockFlow, DisplayItem::SelectionGap, bounds);
     ClipScope clipScope(paintInfo.context);
 
-    LayoutRect gapRectsBounds = m_layoutBlockFlow.selectionGaps(&m_layoutBlockFlow, paintOffset, LayoutSize(), lastTop, lastLeft, lastRight,
-        recorder.canUseCachedDrawing() ? nullptr : &paintInfo,
-        recorder.canUseCachedDrawing() ? nullptr : &clipScope);
+    LayoutRect gapRectsBounds = m_layoutBlockFlow.selectionGaps(&m_layoutBlockFlow, paintOffset, LayoutSize(), lastTop, lastLeft, lastRight, &paintInfo, &clipScope);
     // TODO(wkorman): Rework below to process paint invalidation rects during layout rather than paint.

[Xianzhu, 2015/07/03 01:24:41]

If this TODO is still valid, then we can't early return here. Otherwise we
should remove the TODO. I guess it's still valid.

[pdr., 2015/07/03 02:38:04]

Good catch. Fixing this required a small amount of logic. We now use
Optional<DrawingRecorder> to skip the creation of the recorder when the cache is
used, but still create it when the cache is not used. There are some simple
optimizations we can make here but I opted to keep this as simple as possible
because wkorman will be removing selection rects soon.

     if (!gapRectsBounds.isEmpty()) {
         DeprecatedPaintLayer* layer = m_layoutBlockFlow.enclosingLayer();
         gapRectsBounds.moveBy(-paintOffset);
         if (!m_layoutBlockFlow.hasLayer()) {
             LayoutRect localBounds(gapRectsBounds);
             m_layoutBlockFlow.flipForWritingMode(localBounds);
             gapRectsBounds = LayoutRect(m_layoutBlockFlow.localToContainerQuad(FloatRect(localBounds), layer->layoutObject()).enclosingBoundingBox());
             if (layer->layoutObject()->hasOverflowClip())
                 gapRectsBounds.move(layer->layoutBox()->scrolledContentOffset());
         }
         layer->addBlockSelectionGapsBounds(gapRectsBounds);
     }
 }
 
 } // namespace blink