Fix slimming paint clipping and add a debug fill color

Source/core/paint/BlockPainter.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/BlockPainter.h"
 
 #include "core/editing/Caret.h"
 #include "core/editing/FrameSelection.h"
 #include "core/frame/LocalFrame.h"
@@ skipping 54 matching lines @@
         m_renderBlock.paintObject(paintInfo, adjustedPaintOffset);
     }
     // FIXME: move popContentsClip out of RenderBox.
     if (pushedClip)
         m_renderBlock.popContentsClip(paintInfo, phase, adjustedPaintOffset);
 
     // Our scrollbar widgets paint exactly when we tell them to, so that they work properly with
     // z-index. We paint after we painted the background/border, so that the scrollbars will
     // sit above the background/border.
     if (m_renderBlock.hasOverflowClip() && m_renderBlock.style()->visibility() == VISIBLE && (phase == PaintPhaseBlockBackground || phase == PaintPhaseChildBlockBackground) && paintInfo.shouldPaintWithinRoot(&m_renderBlock) && !paintInfo.paintRootBackgroundOnly()) {
-        PaintCommandRecorder recorder(paintInfo.context, &m_renderBlock, paintInfo.phase, m_renderBlock.visualOverflowRect());
+        PaintCommandRecorder recorder(paintInfo.context, &m_renderBlock, paintInfo.phase, pixelSnappedIntRect(adjustedPaintOffset, m_renderBlock.visualOverflowRect().size()));
         m_renderBlock.layer()->scrollableArea()->paintOverflowControls(paintInfo.context, roundedIntPoint(adjustedPaintOffset), paintInfo.rect, false /* paintingOverlayControls */);
     }
 }
 
 void BlockPainter::paintChildren(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
     for (RenderBox* child = m_renderBlock.firstChildBox(); child; child = child->nextSiblingBox())
         paintChild(child, paintInfo, paintOffset);
 }
 
@@ skipping 51 matching lines @@
         renderer->paint(info, childPoint);
         info.phase = PaintPhaseOutline;
         renderer->paint(info, childPoint);
     }
 }
 
 void BlockPainter::paintObject(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
     PaintPhase paintPhase = paintInfo.phase;
 
-    LayoutRect bounds;
-    if (RuntimeEnabledFeatures::slimmingPaintEnabled())
-        bounds = m_renderBlock.visualOverflowRect();
-
     // Adjust our painting position if we're inside a scrolled layer (e.g., an overflow:auto div).
     LayoutPoint scrolledOffset = paintOffset;
     if (m_renderBlock.hasOverflowClip())
         scrolledOffset.move(-m_renderBlock.scrolledContentOffset());
 
+    LayoutRect bounds;
+    if (RuntimeEnabledFeatures::slimmingPaintEnabled()) {
+        bounds = m_renderBlock.visualOverflowRect();
+        bounds.moveBy(scrolledOffset);
+    }
+
     // 1. paint background, borders etc
     if ((paintPhase == PaintPhaseBlockBackground || paintPhase == PaintPhaseChildBlockBackground) && m_renderBlock.style()->visibility() == VISIBLE) {
         if (m_renderBlock.hasBoxDecorationBackground()) {
             PaintCommandRecorder recorder(paintInfo.context, &m_renderBlock, paintPhase, bounds);
             m_renderBlock.paintBoxDecorationBackground(paintInfo, paintOffset);
         }
         if (m_renderBlock.hasColumns() && !paintInfo.paintRootBackgroundOnly()) {
             // FIXME: PaintCommandRecorder needs to learn to handle this.
             paintColumnRules(paintInfo, scrolledOffset);
         }
@@ skipping 344 matching lines @@
         RenderBlock* block = flow->containingBlock();
         for ( ; block && block != &m_renderBlock; block = block->containingBlock())
             accumulatedPaintOffset.moveBy(block->location());
         ASSERT(block);
         InlinePainter(*flow).paintOutline(info, accumulatedPaintOffset);
     }
 }
 
 
 } // namespace blink