Make copyToVector() robust against conservative GCs.

third_party/WebKit/Source/wtf/Vector.h

Index: third_party/WebKit/Source/wtf/Vector.h
diff --git a/third_party/WebKit/Source/wtf/Vector.h b/third_party/WebKit/Source/wtf/Vector.h
index 73301493c4293be9d76ee4a646fb6204dc53b715..f1387c8dfd904efdfc4d79e240983af36e081e1f 100644
--- a/third_party/WebKit/Source/wtf/Vector.h
+++ b/third_party/WebKit/Source/wtf/Vector.h
@@ -805,6 +805,19 @@ public:
 
     template <typename VisitorDispatcher> void trace(VisitorDispatcher);
 
+    class GCForbiddenScope {
+        STACK_ALLOCATED();
+    public:
+        GCForbiddenScope()
+        {
+            Allocator::enterGCForbiddenScope();
+        }
+        ~GCForbiddenScope()
+        {
+            Allocator::leaveGCForbiddenScope();
+        }
+    };
+
 protected:
     using Base::checkUnusedSlots;
     using Base::clearUnusedSlots;