Special-case LocalDOMWindow for same-origin access in bindings.

third_party/WebKit/Source/modules/compositorworker/WindowAnimationWorklet.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "modules/compositorworker/WindowAnimationWorklet.h"
 
 #include "core/dom/Document.h"
 #include "core/frame/LocalDOMWindow.h"
 #include "core/frame/LocalFrame.h"
-#include "modules/compositorworker/AnimationWorklet.h"
 
 namespace blink {
 
-WindowAnimationWorklet::WindowAnimationWorklet(LocalDOMWindow& window)
-    : ContextLifecycleObserver(window.frame()->document()) {}
-
-const char* WindowAnimationWorklet::supplementName() {
-  return "WindowAnimationWorklet";
-}
-
 // static
-WindowAnimationWorklet& WindowAnimationWorklet::from(LocalDOMWindow& window) {
-  WindowAnimationWorklet* supplement = static_cast<WindowAnimationWorklet*>(
-      Supplement<LocalDOMWindow>::from(window, supplementName()));
-  if (!supplement) {
-    supplement = new WindowAnimationWorklet(window);
-    provideTo(window, supplementName(), supplement);
-  }
-  return *supplement;
-}
-
-// static
-Worklet* WindowAnimationWorklet::animationWorklet(DOMWindow& window) {
+AnimationWorklet* WindowAnimationWorklet::animationWorklet(
+    LocalDOMWindow& window) {
   if (!window.frame())
     return nullptr;
-  return from(toLocalDOMWindow(window))
-      .animationWorklet(toLocalDOMWindow(window));
-}
-
-AnimationWorklet* WindowAnimationWorklet::animationWorklet(
-    LocalDOMWindow& window) {
-  if (!m_animationWorklet && getExecutionContext()) {
-    DCHECK(window.frame());
-    m_animationWorklet = AnimationWorklet::create(window.frame());

[dcheng, 2017/02/01 07:22:59]

This helper got moved into the constructor: there's no point in having it
separate, because when we create it, this will always be executed anyway (the
execution context should still be live).

-  }
-  return m_animationWorklet.get();
+  return from(window).m_animationWorklet.get();
 }
 
 // Break the following cycle when the context gets detached.
 // Otherwise, the worklet object will leak.
+// TODO(dcheng): Why isn't this just all on the Oilpan heap?

[dcheng, 2017/02/01 07:22:59]

Something that might be good to fix... not really sure why this isn't just all
in Oilpan. As far as I can tell, everything lives inside Blink.

[haraken, 2017/02/01 08:32:01]

I'm not sure how easy it will be to move ThreadedWorkletMessagingProxy to Oilpan
since it's handling a bunch of cross-thread complicated pointers and thread
lifetime issues.

Also, even if we move ThreadedWorkletMessagingProxy to Oilpan, it won't solve
the cycle issue because we need to use CrossThreadPersistent to have a
cross-thread reference.

[dcheng, 2017/02/01 18:30:28]

OK, removed the TODO. It feels like it's harder than it has to be, but maybe
this doesn't affect a lot of things.

 //
 // window => window.animationWorklet
 // => WindowAnimationWorklet
 // => AnimationWorklet  <--- break this reference
 // => ThreadedWorkletMessagingProxy
 // => Document
 // => ... => window
 void WindowAnimationWorklet::contextDestroyed(ExecutionContext*) {
   m_animationWorklet = nullptr;
 }
 
 DEFINE_TRACE(WindowAnimationWorklet) {
   visitor->trace(m_animationWorklet);
   Supplement<LocalDOMWindow>::trace(visitor);
   ContextLifecycleObserver::trace(visitor);
 }
 
+// static
+WindowAnimationWorklet& WindowAnimationWorklet::from(LocalDOMWindow& window) {
+  WindowAnimationWorklet* supplement = static_cast<WindowAnimationWorklet*>(
+      Supplement<LocalDOMWindow>::from(window, supplementName()));
+  if (!supplement) {
+    supplement = new WindowAnimationWorklet(window);
+    provideTo(window, supplementName(), supplement);
+  }
+  return *supplement;
+}
+
+WindowAnimationWorklet::WindowAnimationWorklet(LocalDOMWindow& window)
+    : ContextLifecycleObserver(window.frame()->document()),
+      m_animationWorklet(AnimationWorklet::create(window.frame())) {}
+
+const char* WindowAnimationWorklet::supplementName() {
+  return "WindowAnimationWorklet";
+}
+
 }  // namespace blink