Initial PaintInvalidationState support for SVG

Source/core/rendering/svg/RenderSVGModelObject.cpp

Index: Source/core/rendering/svg/RenderSVGModelObject.cpp
diff --git a/Source/core/rendering/svg/RenderSVGModelObject.cpp b/Source/core/rendering/svg/RenderSVGModelObject.cpp
index daeb2eedbac4cead26264887a974a5195655608a..0269301855984e9f2ca1d5addb06d74b79f23eb4 100644
--- a/Source/core/rendering/svg/RenderSVGModelObject.cpp
+++ b/Source/core/rendering/svg/RenderSVGModelObject.cpp
@@ -125,11 +125,20 @@ 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