Put SVGResourceContainer subtypes into their own property trees.

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

Index: third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h
diff --git a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h
index c55aeb1641b0f9f06de2daca0f86c810398088d2..ef96bb0ba7c669079a537e2cffd341c1728b3d9a 100644
--- a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h
+++ b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h
@@ -159,6 +159,9 @@ class PaintPropertyTreeBuilder {
   ALWAYS_INLINE static void updateOutOfFlowContext(
       const LayoutObject&,
       PaintPropertyTreeBuilderContext&);
+
+  // Resets everything to to point at the root property tree nodes.
+  ALWAYS_INLINE void resetToRootContext(PaintPropertyTreeBuilderContext&);
 };
 
 }  // namespace blink