Prepare WindowProxy for using v8::Context::NewRemoteContext().

third_party/WebKit/Source/bindings/core/v8/WindowProxy.h

Index: third_party/WebKit/Source/bindings/core/v8/WindowProxy.h
diff --git a/third_party/WebKit/Source/bindings/core/v8/WindowProxy.h b/third_party/WebKit/Source/bindings/core/v8/WindowProxy.h
index 0a52e8e7e0847ac7350cd41514e3460c60fca5f1..f0771472661215df06daac7140ece13a2cc96c92 100644
--- a/third_party/WebKit/Source/bindings/core/v8/WindowProxy.h
+++ b/third_party/WebKit/Source/bindings/core/v8/WindowProxy.h
@@ -33,7 +33,7 @@
 
 #include "bindings/core/v8/DOMWrapperWorld.h"
 #include "bindings/core/v8/ScopedPersistent.h"
-#include "bindings/core/v8/ScriptState.h"
+#include "core/CoreExport.h"
 #include "platform/heap/Handle.h"
 #include "v8/include/v8.h"
 #include "wtf/RefPtr.h"
@@ -41,25 +41,98 @@
 namespace blink {
 
 class Frame;
-class ScriptController;
 
-// WindowProxy represents all the per-global object state for a Frame that
-// persist between navigations.
+// WindowProxy implements the split window model of a window for a frame. In the
+// HTML standard, the split window model is composed of the Window interface
+// (the inner global object) and the WindowProxy interface (the outer global
+// proxy).
+//
+// The Window interface is backed by the Blink DOMWindow C++ implementation.
+// In contrast, the WindowProxy interface does not have a corresponding
+// C++ implementation in Blink: the WindowProxy class defined here only manages
+// context initialization and detach. Instead, the behavior of the WindowProxy
+// interface is defined by JSGlobalProxy in v8 and the prototype chain set up
+// during context initialization.
+//
+// ====== Inner Global Object ======
+// The inner global object is the global for the script environment of a Frame.
+// Since Window and Document also have a 1:1 relationship, this means that each
+// inner global object has an associated Document which does not change. On
+// navigation, the new Document receives a new inner global object.
+//
+// However, there is one exception to the 1:1 DOMWindow:Document rule. If:
+// - the previous Document is the initial empty document
+// - the new Document is same-origin to the previous Document
+// then the inner global object will be reused for the new Document. This is the
+// only case where the associated Document of an inner global object can change.
+//
+// All methods and attributes defined on the Window interface are exposed via
+// the inner global object. Global variables defined by script running in the
+// Document also live on the inner global object.
+//
+// ====== Outer Global Proxy ====
+// The outer global proxy is reused across navigations. It implements the
+// security checks for same-origin/cross-origin access to the Window interface.
+// When the check passes (i.e. the access is same-origin), the access is
+// forwarded to the inner global object of the active Document in this
+// WindowProxy's Frame).
+//
+// When the security check fails, the access is delegated to the outer global
+// proxy's cross-origin interceptors. The cross-origin interceptors may choose
+// to return a value (if the property is exposed cross-origin) or throw an
+// exception otherwise.
+//
+// Note that the cross-origin interceptors are only used for cross-origin
+// accesses: a same-origin access to a method that is available cross-origin,
+// such as Window.postMessage, will be delegated to the inner global object.
+//
+// ====== LocalWindowProxy vs RemoteWindowProxy ======
+// WindowProxy has two concrete subclasses:
+// - LocalWindowProxy: implements the split window model for a frame in the same
+//   process, i.e. a LocalFrame.
+// - RemoteWindowProxy: implements the split window model for a frame in a
+//   different process, i.e. a RemoteFrame.
+//
+// While having a RemoteFrame implies the frame must be cross-origin, the
+// opposite is not true: a LocalFrame can be same-origin or cross-origin. One
+// additional complexity (which slightly violates the HTML standard): it is
+// possible to have SecurityOrigin::canAccess() return true for a RemoteFrame's
+// security origin; however, it is important to still deny access as if the
+// frame were cross-origin. This is due to complexities in the process
+// allocation model for renderer processes. See https://crbug.com/601629.
+//
+// ====== LocalWindowProxy/RemoteWindowProxy ======
+// Currently, the prototype chain for LocalWindowProxy and RemoteWindowProxy
+// look the same:
+//
+//   outer global proxy
+//     -- has prototype --> inner global object
+//     -- has prototype --> Window.prototype
+//     -- has prototype --> WindowProperties [1]
+//     -- has prototype --> EventTarget.prototype
+//     -- has prototype --> Object.prototype
+//     -- has prototype --> null
+//
+// [1] WindowProperties is the named properties object of the Window interface.
+//
+// There is work in progress to refactor RemoteWindowProxy to use remote v8
+// contexts, to reduce the overhead of remote frames.
+//
+// ====== References ======
+// https://wiki.mozilla.org/Gecko:SplitWindow
+// https://whatwg.org/C/browsers.html#the-windowproxy-exotic-object
 class WindowProxy : public GarbageCollectedFinalized<WindowProxy> {
  public:
   virtual ~WindowProxy();
 
   DECLARE_TRACE();
 
-  v8::Local<v8::Context> contextIfInitialized() const {
-    return m_scriptState ? m_scriptState->context() : v8::Local<v8::Context>();
-  }
   void initializeIfNeeded();
 
   void clearForClose();
   void clearForNavigation();
 
-  v8::Local<v8::Object> globalIfNotDetached();
+  CORE_EXPORT v8::Local<v8::Object> globalIfNotDetached();
   v8::Local<v8::Object> releaseGlobal();
   void setGlobal(v8::Local<v8::Object>);
 
@@ -68,10 +141,6 @@ class WindowProxy : public GarbageCollectedFinalized<WindowProxy> {
   DOMWrapperWorld& world() { return *m_world; }
 
  protected:
-  // TODO(dcheng): Remove this friend declaration once LocalWindowProxyManager
-  // and ScriptController are merged.
-  friend class ScriptController;
-
   // A valid transition is from ContextUninitialized to ContextInitialized,
   // and then ContextDetached. Other transitions are forbidden.
   enum class Lifecycle {
@@ -85,24 +154,24 @@ class WindowProxy : public GarbageCollectedFinalized<WindowProxy> {
   virtual void initialize() = 0;
 
   enum GlobalDetachmentBehavior { DoNotDetachGlobal, DetachGlobal };
-  virtual void disposeContext(GlobalDetachmentBehavior);
-
-  // Associates the window wrapper and its prototype chain with the native
-  // DOMWindow object.  Also does some more Window-specific initialization.
-  void setupWindowPrototypeChain();
+  virtual void disposeContext(GlobalDetachmentBehavior) = 0;
 
   v8::Isolate* isolate() const { return m_isolate; }
   Frame* frame() const { return m_frame.get(); }
-  ScriptState* getScriptState() const { return m_scriptState.get(); }
+
+#if DCHECK_IS_ON()
+  void didAttachGlobalProxy() { m_isGlobalProxyAttached = true; }
+  void didDetachGlobalProxy() { m_isGlobalProxyAttached = false; }
+#endif
 
  private:
   v8::Isolate* const m_isolate;
   const Member<Frame> m_frame;
+#if DCHECK_IS_ON()
+  bool m_isGlobalProxyAttached = false;
+#endif
 
  protected:
-  // TODO(dcheng): Move this to LocalWindowProxy once RemoteWindowProxy uses
-  // remote contexts.
-  RefPtr<ScriptState> m_scriptState;
   // TODO(dcheng): Consider making these private and using getters.
   const RefPtr<DOMWrapperWorld> m_world;
   ScopedPersistent<v8::Object> m_globalProxy;