Fix slimming paint clipping and add a debug fill color

The Slimming Paint codepath wasn't properly adding paint offsets
to the applied clip rects, causing only a fraction of text to be
drawn. Also adding a debug red background to make it more obvious
when we're failing to paint. Cribbed from FrameView's old paint
code.

BUG=423071

Review URL: https://codereview.chromium.org/654713003

git-svn-id: svn://svn.chromium.org/blink/trunk@183634 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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

@@ -72,7 +72,7 @@ void BlockPainter::paint(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
     // 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 */);
     }
 }
@@ -144,15 +144,17 @@ void BlockPainter::paintObject(PaintInfo& paintInfo, const LayoutPoint& paintOff
 {
     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()) {

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

@@ -33,7 +33,7 @@ void LineBoxListPainter::paint(RenderBoxModelObject* renderer, PaintInfo& paintI
         return;
 
     PaintInfo info(paintInfo);
-    PaintCommandRecorder recorder(paintInfo.context, renderer, paintInfo.phase, renderer->borderBoundingBox());
+    PaintCommandRecorder recorder(paintInfo.context, renderer, paintInfo.phase, pixelSnappedIntRect(paintOffset, renderer->borderBoundingBox().size()));
     ListHashSet<RenderInline*> outlineObjects;
     info.setOutlineObjects(&outlineObjects);
 

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

@@ -37,7 +37,7 @@ const PaintCommandList& ViewDisplayList::paintCommandList()
     ASSERT(RuntimeEnabledFeatures::slimmingPaintEnabled());
 
     updatePaintCommandList();
-    return m_paintList;
+    return m_newPaints;
 }
 
 void ViewDisplayList::add(WTF::PassOwnPtr<AtomicPaintChunk> atomicPaintChunk)

third_party/WebKit/Source/core/rendering/compositing/CompositedLayerMapping.cpp

@@ -2134,6 +2134,11 @@ void CompositedLayerMapping::doPaintTask(const GraphicsLayerPaintInfo& paintInfo
         LayerPainter(*paintInfo.renderLayer).paintLayerContents(context, paintingInfo, paintLayerFlags);
 
         if (RuntimeEnabledFeatures::slimmingPaintEnabled()) {
+
+#ifndef NDEBUG
+            context->fillRect(dirtyRect, Color(0xFF, 0, 0));
+#endif
+
             if (RenderView* view = paintInfo.renderLayer->renderer()->view()) {
                 const PaintCommandList& paintCommandList = view->viewDisplayList().paintCommandList();
                 for (PaintCommandList::const_iterator it = paintCommandList.begin(); it != paintCommandList.end(); ++it)