Remove ContextClient from NavigatorMIDI

third_party/WebKit/Source/modules/webmidi/NavigatorWebMIDI.cpp

 /*
  * Copyright (C) 2013 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 24 matching lines @@
 #include "core/dom/DOMException.h"
 #include "core/dom/Document.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Navigator.h"
 #include "core/frame/UseCounter.h"
 #include "modules/webmidi/MIDIAccessInitializer.h"
 #include "modules/webmidi/MIDIOptions.h"
 
 namespace blink {
 
-NavigatorWebMIDI::NavigatorWebMIDI(LocalFrame* frame) : ContextClient(frame) {}
+NavigatorWebMIDI::NavigatorWebMIDI(Navigator& navigator)
+    : Supplement<Navigator>(navigator) {}
 
 DEFINE_TRACE(NavigatorWebMIDI) {
   Supplement<Navigator>::trace(visitor);
-  ContextClient::trace(visitor);
 }
 
 const char* NavigatorWebMIDI::supplementName() {
   return "NavigatorWebMIDI";
 }
 
 NavigatorWebMIDI& NavigatorWebMIDI::from(Navigator& navigator) {
   NavigatorWebMIDI* supplement = static_cast<NavigatorWebMIDI*>(
       Supplement<Navigator>::from(navigator, supplementName()));
   if (!supplement) {
-    supplement = new NavigatorWebMIDI(navigator.frame());
+    supplement = new NavigatorWebMIDI(navigator);
     provideTo(navigator, supplementName(), supplement);
   }
   return *supplement;
 }
 
 ScriptPromise NavigatorWebMIDI::requestMIDIAccess(ScriptState* scriptState,
                                                   Navigator& navigator,
                                                   const MIDIOptions& options) {
   return NavigatorWebMIDI::from(navigator).requestMIDIAccess(scriptState,
                                                              options);
 }
 
 ScriptPromise NavigatorWebMIDI::requestMIDIAccess(ScriptState* scriptState,
                                                   const MIDIOptions& options) {
-  if (!frame() || frame()->document()->isContextDestroyed()) {
+  if (!scriptState->contextIsValid()) {

[haraken, 2017/01/06 01:11:19]

This is "mostly" equivalent to the previous check (except a very subtle
scenario).

[sof, 2017/01/06 07:33:33]

If |scriptState| represents the script state of the caller (with its document
etc), but what was here previously was that of the frame&document of the object,
it seems like it differs quite a bit. Is that the case?

[haraken, 2017/01/06 08:13:35]

I think the two frames should match. The user script is calling
navigator.requestMIDIAccess. Then in the C++ callback for requestMIDIAccess,
ScriptState::current() returns the ScriptState of the navigator object. So they
should match (in theory).

Also below we're calling MIDIAccessInitializer::start(scriptState, options),
which indicates that it's better to validate ScriptState rather than frame() or
document().

[sof, 2017/01/06 10:21:20]

agreed, thanks for clarifying.

     return ScriptPromise::rejectWithDOMException(
         scriptState,
         DOMException::create(AbortError, "The frame is not working."));
   }
 
-  UseCounter::countCrossOriginIframe(*frame()->document(),
-                                     UseCounter::RequestMIDIAccessIframe);
+  UseCounter::countCrossOriginIframe(
+      *toDocument(scriptState->getExecutionContext()),
+      UseCounter::RequestMIDIAccessIframe);
   return MIDIAccessInitializer::start(scriptState, options);
 }
 
 }  // namespace blink