Subtree caching implementation in blink-core

Source/core/paint/DeprecatedPaintLayerPainter.cpp

Index: Source/core/paint/DeprecatedPaintLayerPainter.cpp
diff --git a/Source/core/paint/DeprecatedPaintLayerPainter.cpp b/Source/core/paint/DeprecatedPaintLayerPainter.cpp
index 2f5156751e7f103a59518343cbc82251c37479d3..1b317da518dc942cd6652c8ae96bfb32fb79d23d 100644
--- a/Source/core/paint/DeprecatedPaintLayerPainter.cpp
+++ b/Source/core/paint/DeprecatedPaintLayerPainter.cpp
@@ -26,6 +26,7 @@
 #include "platform/graphics/paint/ClipPathRecorder.h"
 #include "platform/graphics/paint/ClipRecorder.h"
 #include "platform/graphics/paint/CompositingDisplayItem.h"
+#include "platform/graphics/paint/SubsequenceRecorder.h"
 #include "platform/graphics/paint/Transform3DDisplayItem.h"
 #include "wtf/Optional.h"
 
@@ -68,8 +69,13 @@ void DeprecatedPaintLayerPainter::paintLayer(GraphicsContext* context, const Dep
     }
 
     // Non self-painting leaf layers don't need to be painted as their layoutObject() should properly paint itself.
-    if (!m_paintLayer.isSelfPaintingLayer() && !m_paintLayer.hasSelfPaintingLayerDescendant())
+    if (!m_paintLayer.isSelfPaintingLayer() && !m_paintLayer.hasSelfPaintingLayerDescendant()) {
+        ASSERT(!m_paintLayer.needsRepaint());
         return;
+    }
+
+    bool needsRepaint = m_paintLayer.needsRepaint();
+    m_paintLayer.clearNeedsRepaint();
 
     if (shouldSuppressPaintingLayer(&m_paintLayer))
         return;
@@ -78,6 +84,10 @@ void DeprecatedPaintLayerPainter::paintLayer(GraphicsContext* context, const Dep
     if (!m_paintLayer.layoutObject()->opacity())
         return;
 
+    if (!needsRepaint && SubsequenceRecorder::useCachedSubsequenceIfPossible(*context, *m_paintLayer.layoutObject()))

[chrishtr, 2015/08/27 04:29:48]

Why aren't you checking for being a stacking context?

[Xianzhu, 2015/08/27 16:38:02]

Adding condition for stacking context seems just to complicate and cause missing
of some chances of relatively independently painted subsequences e.g for
non-stacking-context overflow:scroll divs.

+        return;
+    SubsequenceRecorder subsequenceRecorder(*context, *m_paintLayer.layoutObject());
+
     if (m_paintLayer.paintsWithTransparency(paintingInfo.globalPaintFlags()))
         paintFlags |= PaintLayerHaveTransparency;