Initial PaintInvalidationState support for SVG

Source/core/rendering/svg/RenderSVGModelObject.cpp

 /*
  * Copyright (c) 2009, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
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@@ skipping 107 matching lines @@
     return false;
 }
 
 // The SVG addFocusRingRects() method adds rects in local coordinates so the default absoluteFocusRingQuads
 // returns incorrect values for SVG objects. Overriding this method provides access to the absolute bounds.
 void RenderSVGModelObject::absoluteFocusRingQuads(Vector<FloatQuad>& quads)
 {
     quads.append(localToAbsoluteQuad(FloatQuad(paintInvalidationRectInLocalCoordinates())));
 }
 
-InvalidationReason RenderSVGModelObject::invalidatePaintIfNeeded(const PaintInvalidationState& paintInvalidationState, const RenderLayerModelObject& paintInvalidationContainer)
+void RenderSVGModelObject::invalidateTreeIfNeeded(const PaintInvalidationState& paintInvalidationState)
 {
-    ForceHorriblySlowRectMapping slowRectMapping(&paintInvalidationState);
+    ASSERT(!needsLayout());
 
-    return RenderObject::invalidatePaintIfNeeded(paintInvalidationState, paintInvalidationContainer);
+    // If we didn't need paint invalidation then our children don't need as well.

[pdr., 2014/09/25 05:38:59]

Nit: In my experience, children are extremely needy.

[fs, 2014/09/25 12:17:53]

My diplomatic response to this would be: "No comment"

On a more serious note, I'm not sure I (fully) agree with this statement, but
AFAIU it's an invariant of the current system. This comment just hitched a ride
from the previous (base-class) impl. in RenderObject.

[fs, 2014/09/25 12:30:26]

s/this statement/the statement the comment makes/ (to avoid confusion)

[dsinclair, 2014/09/25 13:14:11]

As part of repaint-after-layout, we made this an invariant. It's currently
maintained by assertSubtreeClearedPaintInvalidationState() and
assertRendererClearedPaintInvalidationState().

When invalidation is finished we walk over all renderers and ASSERT that the
state is clean. 

+    // Skip walking down the tree as everything should be fine below us.
+    if (!shouldCheckForPaintInvalidation(paintInvalidationState))
+        return;
+
+    invalidatePaintIfNeeded(paintInvalidationState, paintInvalidationState.paintInvalidationContainer());
+    clearPaintInvalidationState(paintInvalidationState);
+
+    PaintInvalidationState childPaintInvalidationState(paintInvalidationState, *this);
+    invalidatePaintOfSubtreesIfNeeded(childPaintInvalidationState);
 }
 
 } // namespace blink