Put SVGResourceContainer subtypes into their own property trees.

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

Index: third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
index 247d41b8d2ed7c8bd5f7a7da7f2b0150a73e79a3..3b7a3de16637380dbc1089ae930a53005d8b889b 100644
--- a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
@@ -26,7 +26,7 @@
 
 namespace blink {
 
-void PaintPropertyTreeBuilder::setupInitialContext(
+void PaintPropertyTreeBuilder::resetToRootContext(
     PaintPropertyTreeBuilderContext& context) {
   context.current.clip = context.absolutePosition.clip =
       context.fixedPosition.clip = ClipPaintPropertyNode::root();
@@ -38,6 +38,11 @@ void PaintPropertyTreeBuilder::setupInitialContext(
       context.fixedPosition.scroll = ScrollPaintPropertyNode::root();
 }
 
+void PaintPropertyTreeBuilder::setupInitialContext(
+    PaintPropertyTreeBuilderContext& context) {
+  resetToRootContext(context);
+}
+
 // True if a new property was created, false if an existing one was updated.
 static bool updatePreTranslation(
     FrameView& frameView,
@@ -1090,6 +1095,13 @@ void PaintPropertyTreeBuilder::updateForObjectLocationAndSize(
 void PaintPropertyTreeBuilder::updatePropertiesForSelf(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
+  if (object.isSVGResourceContainer()) {
+    // SVG resources are painted within one or more other locations in the
+    // SVG during paint, and hence have their own independent paint property
+    // trees.
+    resetToRootContext(context);

[pdr., 2017/03/21 22:26:22]

This re-use of setupInitialContext is clever. I think we will need to make it a
little more robust for your usecase though. For example, paintOffset,
shouldFlattenInheritedTransform, containerForAbsolutePosition, and
paintOffsetForFloat need to be reset.

[chrishtr, 2017/03/21 23:29:57]

Changed to reuse the constructor, which will get these for free.

+  }
+
   // This is not in FindObjectPropertiesNeedingUpdateScope because paint offset
   // can change without needsPaintPropertyUpdate.
   updateForObjectLocationAndSize(object, context);