Make UseCounter take a LocaFrame instead of any Frame

third_party/WebKit/Source/bindings/core/v8/custom/V8WindowCustom.cpp

Index: third_party/WebKit/Source/bindings/core/v8/custom/V8WindowCustom.cpp
diff --git a/third_party/WebKit/Source/bindings/core/v8/custom/V8WindowCustom.cpp b/third_party/WebKit/Source/bindings/core/v8/custom/V8WindowCustom.cpp
index a6e1f06b7c4e9be4b635e4ae76709e528b0dc690..b4256a8940509a96cb8a326347b8ee9f307a2a7b 100644
--- a/third_party/WebKit/Source/bindings/core/v8/custom/V8WindowCustom.cpp
+++ b/third_party/WebKit/Source/bindings/core/v8/custom/V8WindowCustom.cpp
@@ -217,7 +217,7 @@ void V8Window::postMessageMethodCustom(
   LocalDOMWindow* source = CurrentDOMWindow(info.GetIsolate());
 
   DCHECK(window);
-  UseCounter::Count(window->GetFrame(), UseCounter::kWindowPostMessage);
+  UseCounter::Count(source->GetFrame(), UseCounter::kWindowPostMessage);
 
   // If called directly by WebCore we don't have a calling context.
   if (!source) {
@@ -318,7 +318,7 @@ void V8Window::namedPropertyGetterCustom(
   // https://html.spec.whatwg.org/multipage/browsers.html#document-tree-child-browsing-context-name-property-set
   Frame* child = frame->Tree().ScopedChild(name);
   if (child) {
-    UseCounter::Count(window->GetFrame(),
+    UseCounter::Count(CurrentExecutionContext(info.GetIsolate()),

[haraken, 2017/05/15 03:40:45]

This will work as expected because CurrentExecutionContext returns nullptr for a
remote frame and UseCounter::Count ignores the nullptr execution context.

However, I'd prefer using an explicit isLocalFrame check to make the logic
explicit.

[dcheng, 2017/05/15 04:04:02]

I'm not sure I follow: I don't think CurrentExecutionContext() can ever
correspond to a context that belongs to a remote frame (since a remote frame's
context can't be entered).

[haraken, 2017/05/15 04:45:45]

CurrentExecutionContext() returns nullptr for a remote frame. UseCounter::Count
ignores it. As a result, this line is no-op for a remote frame.

I'm just suggesting making the logic more explicit using the IsLocalFrame check.

[dcheng, 2017/05/15 04:57:30]

Right, but CurrentExecutionContext() gets it from
v8::Isolate::GetCurrentContext(), right? It's impossible for v8 to enter a
v8::Context that does not correspond to a LocalFrame.

Thus, even though the bindings code internally looks like it needs to handle the
RemoteFrame case, it's actually impossible. (I agree this is confusing)

                       UseCounter::kNamedAccessOnWindow_ChildBrowsingContext);
 
     // step 3. Remove each browsing context from childBrowsingContexts whose
@@ -332,7 +332,7 @@ void V8Window::namedPropertyGetterCustom(
     }
 
     UseCounter::Count(
-        window->GetFrame(),
+        CurrentExecutionContext(info.GetIsolate()),

[haraken, 2017/05/15 03:40:45]

Ditto.

         UseCounter::
             kNamedAccessOnWindow_ChildBrowsingContext_CrossOriginNameMismatch);
     // In addition to the above spec'ed case, we return the child window