Remove ContextClient from NavigatorMIDI

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

Index: third_party/WebKit/Source/modules/webmidi/NavigatorWebMIDI.cpp
diff --git a/third_party/WebKit/Source/modules/webmidi/NavigatorWebMIDI.cpp b/third_party/WebKit/Source/modules/webmidi/NavigatorWebMIDI.cpp
index 90a04e6c29b2033c88b1c55d1f48758c014ab764..2fb589694c2b765b49ed74d6d8fb50cbc576e41b 100644
--- a/third_party/WebKit/Source/modules/webmidi/NavigatorWebMIDI.cpp
+++ b/third_party/WebKit/Source/modules/webmidi/NavigatorWebMIDI.cpp
@@ -42,11 +42,11 @@
 
 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() {
@@ -57,7 +57,7 @@ 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;
@@ -72,14 +72,15 @@ ScriptPromise NavigatorWebMIDI::requestMIDIAccess(ScriptState* scriptState,
 
 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);
 }