Check rect under-invalidations

third_party/WebKit/Source/platform/graphics/GraphicsLayer.h

Index: third_party/WebKit/Source/platform/graphics/GraphicsLayer.h
diff --git a/third_party/WebKit/Source/platform/graphics/GraphicsLayer.h b/third_party/WebKit/Source/platform/graphics/GraphicsLayer.h
index d1d72afdafb098a350aaa07a649e911fcd9d9568..7f76a59227ebcc95cbd34b15ca24ed2d25101c3b 100644
--- a/third_party/WebKit/Source/platform/graphics/GraphicsLayer.h
+++ b/third_party/WebKit/Source/platform/graphics/GraphicsLayer.h
@@ -210,10 +210,19 @@ public:
     // pointers for the layers and timing data will be included in the returned string.
     String layerTreeAsText(LayerTreeFlags = LayerTreeNormal) const;
 
-    bool isTrackingPaintInvalidations() const { return m_client->isTrackingPaintInvalidations(); }
+    void setTracksPaintInvalidations(bool);
+    bool isTrackingOrCheckingPaintInvalidations() const

[pdr., 2016/06/09 19:21:44]

I worry that the checking part will be very slow on debug bots. Do we need this
to run the pixel verification continuously? I am wondering if we could just do
the pixel verification manually using the flag.

[Xianzhu, 2016/06/09 20:47:44]

If the flag is not enabled, we do pixel verification only in repaint tests which
explicitly track paint invalidations. Most of the tests just track paint
invalidations for just 1 or 2 paintings.

Compared timings of running layout tests under fast/repaint with and without
this patch with debug builds:

With this patch:
12:59:58.361 15624 PER TEST TIME IN TESTSHELL (seconds):
12:59:58.361 15624   Median:           0.590
12:59:58.361 15624   Mean:             0.523
12:59:58.361 15624   90th percentile:  0.776
12:59:58.361 15624   99th percentile:  1.118
12:59:58.361 15624   Standard dev:     0.045
slowest: fast/repaint/4774354.html took 1.5 seconds

Without this patch:
13:35:42.968 23271 PER TEST TIME IN TESTSHELL (seconds):
13:35:42.968 23271   Median:           0.615
13:35:42.968 23271   Mean:             0.540
13:35:42.968 23271   90th percentile:  0.793
13:35:42.968 23271   99th percentile:  1.157
13:35:42.968 23271   Standard dev:     0.052
slowest: fast/repaint/4774354.html took 1.5 seconds

They are basically the same indicating that pixel verification contributes
little to the time.

+    {
+#if DCHECK_IS_ON()
+        if (RuntimeEnabledFeatures::slimmingPaintUnderInvalidationCheckingEnabled())
+            return true;
+#endif
+        return m_isTrackingPaintInvalidations;
+    }
+
     void resetTrackedPaintInvalidations();
     bool hasTrackedPaintInvalidations() const;
-    void trackPaintInvalidation(const DisplayItemClient&, const FloatRect&, PaintInvalidationReason);
+    void trackPaintInvalidation(const DisplayItemClient&, const IntRect&, PaintInvalidationReason);
 
     void addLinkHighlight(LinkHighlight*);
     void removeLinkHighlight(LinkHighlight*);
@@ -292,6 +301,11 @@ private:
     void clearContentsLayerIfUnregistered();
     WebLayer* contentsLayerIfRegistered();
 
+#if DCHECK_IS_ON()
+    PassRefPtr<SkPicture> capturePicture();
+    void checkUnderPaintInvalidations(const SkPicture&);
+#endif
+
     GraphicsLayerClient* m_client;
 
     // Offset from the owning layoutObject
@@ -325,6 +339,8 @@ private:
     bool m_textPainted : 1;
     bool m_imagePainted : 1;
 
+    bool m_isTrackingPaintInvalidations : 1;
+
     GraphicsLayerPaintingPhase m_paintingPhase;
 
     Vector<GraphicsLayer*> m_children;