Skip PaintLayer empty paint phases if it previously painted nothing

third_party/WebKit/Source/core/paint/PaintLayer.h

Index: third_party/WebKit/Source/core/paint/PaintLayer.h
diff --git a/third_party/WebKit/Source/core/paint/PaintLayer.h b/third_party/WebKit/Source/core/paint/PaintLayer.h
index 5c0990c041a44c675a0abb915cfb1d4cff29073b..c7f325cbb9cc8bcc554ab303d11f0aa4f34505cd 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayer.h
+++ b/third_party/WebKit/Source/core/paint/PaintLayer.h
@@ -669,16 +669,36 @@ public:
     void setPreviousPaintResult(PaintLayerPainter::PaintResult result) { m_previousPaintResult = static_cast<unsigned>(result); ASSERT(m_previousPaintResult == static_cast<unsigned>(result)); }
 
     // Used to skip PaintPhaseDescendantOutlinesOnly for layers that have never had descendant outlines.
-    // Once it's set we never clear it because it's not easy to track if all outlines have been removed.
-    bool needsPaintPhaseDescendantOutlines() const { return m_needsPaintPhaseDescendantOutlines; }
-    void setNeedsPaintPhaseDescendantOutlines() { ASSERT(isSelfPaintingLayer()); m_needsPaintPhaseDescendantOutlines = true; }
+    // The flag is set during paint invalidation on a self painting layer if any contained object has outline.
+    // It's cleared during painting if PaintPhaseDescendantOutlinesOnly painted nothing.
+    bool needsPaintPhaseDescendantOutlines() const { return m_needsPaintPhaseDescendantOutlines && !m_previousPaintPhaseDescendantOutlinesWasEmpty; }
+    void setNeedsPaintPhaseDescendantOutlines()
+    {
+        ASSERT(isSelfPaintingLayer());
+        m_needsPaintPhaseDescendantOutlines = true;
+        m_previousPaintPhaseDescendantOutlinesWasEmpty = false;
+    }
+    void setPreviousPaintPhaseDescendantOutlinesEmpty(bool isEmpty) { m_previousPaintPhaseDescendantOutlinesWasEmpty = isEmpty; }
 
     // Similar to above, but for PaintPhaseFloat.
-    bool needsPaintPhaseFloat() const { return m_needsPaintPhaseFloat; }
-    void setNeedsPaintPhaseFloat() { ASSERT(isSelfPaintingLayer()); m_needsPaintPhaseFloat = true; }
+    bool needsPaintPhaseFloat() const { return m_needsPaintPhaseFloat && !m_previousPaintPhaseFloatWasEmpty; }
+    void setNeedsPaintPhaseFloat()
+    {
+        ASSERT(isSelfPaintingLayer());
+        m_needsPaintPhaseFloat = true;
+        m_previousPaintPhaseFloatWasEmpty = false;
+    }
+    void setPreviousPaintPhaseFloatEmpty(bool isEmpty) { m_previousPaintPhaseFloatWasEmpty= isEmpty; }
 
-    bool needsPaintPhaseDescendantBlockBackgrounds() const { return m_needsPaintPhaseDescendantBlockBackgrounds; }
-    void setNeedsPaintPhaseDescendantBlockBackgrounds() { ASSERT(isSelfPaintingLayer()); m_needsPaintPhaseDescendantBlockBackgrounds = true; }
+    // Similar to above, but for PaintPhaseDescendantBlockBackgroundsOnly.
+    bool needsPaintPhaseDescendantBlockBackgrounds() const { return m_needsPaintPhaseDescendantBlockBackgrounds && !m_previousPaintPhaseDescendantBlockBackgroundsWasEmpty; }
+    void setNeedsPaintPhaseDescendantBlockBackgrounds()
+    {
+        ASSERT(isSelfPaintingLayer());
+        m_needsPaintPhaseDescendantBlockBackgrounds = true;
+        m_previousPaintPhaseDescendantBlockBackgroundsWasEmpty = false;
+    }
+    void setPreviousPaintPhaseDescendantBlockBackgroundsEmpty(bool isEmpty) { m_previousPaintPhaseDescendantBlockBackgroundsWasEmpty = isEmpty; }
 
     PaintTiming* paintTiming();
 
@@ -827,8 +847,11 @@ private:
     unsigned m_previousPaintResult : 1; // PaintLayerPainter::PaintResult
 
     unsigned m_needsPaintPhaseDescendantOutlines : 1;
+    unsigned m_previousPaintPhaseDescendantOutlinesWasEmpty : 1;
     unsigned m_needsPaintPhaseFloat : 1;
+    unsigned m_previousPaintPhaseFloatWasEmpty : 1;
     unsigned m_needsPaintPhaseDescendantBlockBackgrounds : 1;
+    unsigned m_previousPaintPhaseDescendantBlockBackgroundsWasEmpty : 1;
 
     // These bitfields are part of ancestor/descendant dependent compositing inputs.
     unsigned m_hasDescendantWithClipPath : 1;