Paint invalidation tests for slimming paint v2

Source/core/testing/Internals.idl

Index: Source/core/testing/Internals.idl
diff --git a/Source/core/testing/Internals.idl b/Source/core/testing/Internals.idl
index 4b24aaf839bd080d0210ac3cb87fc1da0434dab6..d885e696ac2ba89d951856b1f267edd031bfdfa7 100644
--- a/Source/core/testing/Internals.idl
+++ b/Source/core/testing/Internals.idl
@@ -232,6 +232,7 @@
 
     // These functions both reset the tracked repaint rects. They are inteded to be used in the following order:
     //  startTrackingRepaints, repaintRectsAsText, stopTrackingRepaints.
+    // TODO(wangxianzhu): Remove these functions when we no longer use repaint rects.
     [RaisesException, TypeChecking=Interface] void startTrackingRepaints(Document document);
     [RaisesException, TypeChecking=Interface] void stopTrackingRepaints(Document document);
 
@@ -242,6 +243,13 @@
 
     [RaisesException, TypeChecking=Interface] void forceFullRepaint(Document document);
 
+    // These functions both reset the tracked paint invalidation objects. They are inteded to be used in the following order:
+    //  startTrackingPaintInvalidationObjects, paintInvalidationObjects, stopTrackingPaintInvalidationObjects.

[chrishtr, 2015/08/31 22:52:19]

Add a comment that trackedPaintInvalidationObjects() includes a debug string for
each object which was invalidated between start and stop, and may include the
same object multiple times. (the last statement is correct, right?)

[Xianzhu, 2015/08/31 23:04:38]

The last statement is correct.

Done.

+    void startTrackingPaintInvalidationObjects();
+    void stopTrackingPaintInvalidationObjects();
+
+    DOMString[] trackedPaintInvalidationObjects();
+
     // Returns a list of draggable/non-draggable regions in the document.
     [RaisesException, TypeChecking=Interface] ClientRectList draggableRegions(Document document);
     [RaisesException, TypeChecking=Interface] ClientRectList nonDraggableRegions(Document document);