Add methods for creating V8 extras-based ReadableStreams from C++

Source/bindings/core/v8/ScriptState.cpp

 // Copyright 2014 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 "config.h"
 #include "bindings/core/v8/ScriptState.h"
 
 #include "bindings/core/v8/V8Binding.h"
 #include "core/dom/ExecutionContext.h"
 #include "core/frame/LocalDOMWindow.h"
@@ skipping 84 matching lines @@
 
 ScriptValue ScriptState::getFromGlobalObject(const char* name)
 {
     v8::HandleScope handleScope(m_isolate);
     v8::Local<v8::Value> v8Value;
     if (!context()->Global()->Get(context(), v8AtomicString(isolate(), name)).ToLocal(&v8Value))
         return ScriptValue();
     return ScriptValue(this, v8Value);
 }
 
+ScriptValue ScriptState::getFromExtrasExports(const char* name)
+{
+    v8::HandleScope handleScope(m_isolate);
+    v8::Local<v8::Value> v8Value;
+    if (!context()->GetExtrasExportsObject()->Get(context(), v8AtomicString(isolate(), name)).ToLocal(&v8Value))
+        return ScriptValue();
+    return ScriptValue(this, v8Value);
+}
+
 ExecutionContext* ScriptState::executionContext() const
 {
     v8::HandleScope scope(m_isolate);
     return toExecutionContext(context());
 }
 
 void ScriptState::setExecutionContext(ExecutionContext*)
 {
     ASSERT_NOT_REACHED();
 }
@@ skipping 11 matching lines @@
 
 ScriptState* ScriptState::forWorld(LocalFrame* frame, DOMWrapperWorld& world)
 {
     ASSERT(frame);
     v8::Isolate* isolate = toIsolate(frame);
     v8::HandleScope handleScope(isolate);
     return ScriptState::from(toV8ContextEvenIfDetached(frame, world));
 }
 
 }