binding: Changes the association among global-proxy/global/window-instance.

third_party/WebKit/Source/bindings/core/v8/V8GCController.cpp

Index: third_party/WebKit/Source/bindings/core/v8/V8GCController.cpp
diff --git a/third_party/WebKit/Source/bindings/core/v8/V8GCController.cpp b/third_party/WebKit/Source/bindings/core/v8/V8GCController.cpp
index 0d099ccade7b45cb3ee7e2b38107e2ec856cc787..4c0255f49b756c312fa932cfbc2e30371ce90fff 100644
--- a/third_party/WebKit/Source/bindings/core/v8/V8GCController.cpp
+++ b/third_party/WebKit/Source/bindings/core/v8/V8GCController.cpp
@@ -468,7 +468,9 @@ void V8GCController::collectAllGarbageForTesting(v8::Isolate* isolate) {
 
 class DOMWrapperTracer : public v8::PersistentHandleVisitor {
  public:
-  explicit DOMWrapperTracer(Visitor* visitor) : m_visitor(visitor) {}
+  explicit DOMWrapperTracer(Visitor* visitor) : m_visitor(visitor) {
+    DCHECK(m_visitor);
+  }
 
   void VisitPersistentHandle(v8::Persistent<v8::Value>* value,
                              uint16_t classId) override {
@@ -479,8 +481,8 @@ class DOMWrapperTracer : public v8::PersistentHandleVisitor {
     const v8::Persistent<v8::Object>& wrapper =
         v8::Persistent<v8::Object>::Cast(*value);
 
-    if (m_visitor)
-      toWrapperTypeInfo(wrapper)->trace(m_visitor, toScriptWrappable(wrapper));
+    if (ScriptWrappable* scriptWrappable = toScriptWrappable(wrapper))
+      toWrapperTypeInfo(wrapper)->trace(m_visitor, scriptWrappable);
   }
 
  private: