Support for AudioContextOptions latencyHint.

third_party/WebKit/Source/modules/webaudio/AudioContext.h

 // Copyright 2015 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.
 
 #ifndef AudioContext_h
 #define AudioContext_h
 
 #include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptPromiseResolver.h"
+#include "modules/webaudio/AudioContextOptions.h"
 #include "modules/webaudio/BaseAudioContext.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
 class Document;
 class ExceptionState;
 class ScriptState;
 
 // This is an BaseAudioContext which actually plays sound, unlike an
 // OfflineAudioContext which renders sound into a buffer.
-class AudioContext : public BaseAudioContext {
+class MODULES_EXPORT AudioContext : public BaseAudioContext {
   DEFINE_WRAPPERTYPEINFO();
 
  public:
-  static AudioContext* create(Document&, ExceptionState&);
+  static AudioContext* create(Document&,
+                              const AudioContextOptions&,
+                              ExceptionState&);
+  static AudioContext* create(Document&,
+                              const WebAudioLatencyHint&,
+                              ExceptionState&);

[hongchan, 2016/12/02 17:40:11]

This is slightly confusing. Why do we need two different static creators? Isn't
the latency hint a part of the context options?
Please do make comments why we need 2 different creators - but preferably this
needs to be refactored into one.

[Andrew MacPherson, 2016/12/05 14:12:53]

Makes sense, I have refactored this down to 1 static constructor now. The second
one was being used by the BaseAudioContext::create() method which only appears
to be used in the BaseAudioContextTest.

 
   ~AudioContext() override;
   DECLARE_VIRTUAL_TRACE();
 
   ScriptPromise closeContext(ScriptState*);
   bool isContextClosed() const final;
 
   ScriptPromise suspendContext(ScriptState*) final;
   ScriptPromise resumeContext(ScriptState*) final;
 
   bool hasRealtimeConstraint() final { return true; }
 
+  double baseLatency() const;
+
  protected:
-  AudioContext(Document&);
+  AudioContext(Document&, const WebAudioLatencyHint&);
 
   void didClose() final;
 
  private:
   void stopRendering();
 
   unsigned m_contextId;
   Member<ScriptPromiseResolver> m_closeResolver;
 };
 
 }  // namespace blink
 
 #endif  // AudioContext_h