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..ea7979e845475731f6e19908bb957e299d9bd6d5 100644
--- a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h
+++ b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h
@@ -90,11 +90,8 @@ struct PaintPropertyTreeBuilderContext {
   // property tree changes (i.e., a node is added or removed).
   bool forceSubtreeUpdate;
 
-  PaintPropertyTreeBuilderContext()
-      : containerForAbsolutePosition(nullptr),
-        currentEffect(nullptr),
-        inputClipOfCurrentEffect(nullptr),
-        forceSubtreeUpdate(false) {}
+  // Initializes all property tree nodes to the roots.
+  PaintPropertyTreeBuilderContext();
 };
 
 // Creates paint property tree nodes for special things in the layout tree.