[Blink, RemotePlaybackAPI] Create WebRemotePlaybackClient in HTMLMediaElement ctor to avoid lazy in…

third_party/WebKit/Source/core/html/HTMLMediaElement.cpp

 /*
  * Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights
  * reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 78 matching lines @@
 #include "public/platform/WebInbandTextTrack.h"
 #include "public/platform/WebMediaPlayerSource.h"
 #include "public/platform/WebMediaStream.h"
 #include "public/platform/modules/remoteplayback/WebRemotePlaybackClient.h"
 #include "public/platform/modules/remoteplayback/WebRemotePlaybackState.h"
 #include "wtf/CurrentTime.h"
 #include "wtf/MathExtras.h"
 #include "wtf/PtrUtil.h"
 #include "wtf/text/CString.h"
 #include <limits>
+#include <v8.h>
 
 #ifndef BLINK_MEDIA_LOG
 #define BLINK_MEDIA_LOG DVLOG(3)
 #endif
 
 #ifndef LOG_MEDIA_EVENTS
 // Default to not logging events because so many are generated they can
 // overwhelm the rest of the logging.
 #define LOG_MEDIA_EVENTS 0
 #endif
@@ skipping 359 matching lines @@
   BLINK_MEDIA_LOG << "HTMLMediaElement(" << (void*)this << ")";
 
   // If any experiment is enabled, then we want to enable a user gesture by
   // default, otherwise the experiment does nothing.
   if ((document.settings() &&
        document.settings()->mediaPlaybackRequiresUserGesture()) ||
       m_autoplayHelper->isExperimentEnabled()) {
     m_lockedPendingUserGesture = true;
   }
 
+  LocalFrame* frame = document.frame();
+  if (frame) {
+    v8::Isolate* isolate = v8::Isolate::GetCurrent();
+    ScriptState* scriptState = ScriptState::from(isolate->GetCurrentContext());

[haraken, 2016/11/08 23:50:40]

You shouldn't use isolate->GetCurrentContext() unless you're pretty sure that
this code is always called while you're already in a correct context.

Instead, you can pass in a ScriptState* parameter using
[ConstructorCallWith=ScriptState].

(Actually passing ScriptState* to HTMLMediaElement and then to RemotePlayback is
wrong for a complicated reason
(https://groups.google.com/a/chromium.org/d/topic/platform-architecture-dev/nB...),
but that's a separate discussion.)

[whywhat, 2016/11/09 00:22:02]

Tests actually crash because context seems to be empty when the document is
being parsed and HTMLMediaElement is being created.
So in my case I only keep ScriptState to run an async callback. Should I try to
pass ScriptState to the callback then? Does ScriptState support being passed
around like a bound object?

+    m_remotePlaybackClient =
+        frame->loader().client()->createWebRemotePlaybackClient(scriptState,
+                                                                *this);
+  }
+
   setHasCustomStyleCallbacks();
   addElementToDocumentMap(this, &document);
 
   UseCounter::count(document, UseCounter::HTMLMediaElement);
 }
 
 HTMLMediaElement::~HTMLMediaElement() {
   BLINK_MEDIA_LOG << "~HTMLMediaElement(" << (void*)this << ")";
 
   // m_audioSourceNode is explicitly cleared by AudioNode::dispose().
@@ skipping 3444 matching lines @@
 
 void HTMLMediaElement::notifyPositionMayHaveChanged(
     const IntRect& visibleRect) {
   m_autoplayHelper->positionChanged(visibleRect);
 }
 
 void HTMLMediaElement::updatePositionNotificationRegistration() {
   m_autoplayHelper->updatePositionNotificationRegistration();
 }
 
-void HTMLMediaElement::setRemotePlaybackClient(
-    WebRemotePlaybackClient* client) {
-  m_remotePlaybackClient = client;
-}
-
 // TODO(liberato): remove once autoplay gesture override experiment concludes.
 void HTMLMediaElement::triggerAutoplayViewportCheckForTesting() {
   if (FrameView* view = document().view())
     m_autoplayHelper->positionChanged(
         view->rootFrameToContents(view->computeVisibleArea()));
   m_autoplayHelper->triggerAutoplayViewportCheckForTesting();
 }
 
 void HTMLMediaElement::scheduleResolvePlayPromises() {
   // TODO(mlamouri): per spec, we should create a new task but we can't create
@@ skipping 221 matching lines @@
 
 IntRect HTMLMediaElement::AutoplayHelperClientImpl::absoluteBoundingBoxRect()
     const {
   IntRect result;
   if (LayoutObject* object = m_element->layoutObject())
     result = object->absoluteBoundingBoxRect();
   return result;
 }
 
 }  // namespace blink