Implement suspend/resume for AudioContext

Source/modules/webaudio/AudioContext.h

Index: Source/modules/webaudio/AudioContext.h
diff --git a/Source/modules/webaudio/AudioContext.h b/Source/modules/webaudio/AudioContext.h
index fde6ef7ed7740ff95a48abdf0ce71b0919cf28bc..021168019b2129b36a502dc25768272d78bd85e7 100644
--- a/Source/modules/webaudio/AudioContext.h
+++ b/Source/modules/webaudio/AudioContext.h
@@ -25,6 +25,8 @@
 #ifndef AudioContext_h
 #define AudioContext_h
 
+#include "bindings/core/v8/ScriptPromise.h"
+#include "bindings/core/v8/ScriptPromiseResolver.h"
 #include "core/dom/ActiveDOMObject.h"
 #include "core/events/EventListener.h"
 #include "modules/EventTargetModules.h"
@@ -77,6 +79,16 @@ class AudioContext : public RefCountedGarbageCollectedWillBeGarbageCollectedFina
     DEFINE_WRAPPERTYPEINFO();
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(AudioContext);
 public:
+    // The state of an audio context.  On creation, the state is Paused. The state is Running if
+    // audio is being processed (audio graph is being pulled for data). The state is Released if the
+    // audio context has been released.  The valid transitions are from Paused to either Running or
+    // Released; Running to Paused or Released. Once Released, there are no valid transitions.
+    enum AudioContextState {
+        Paused,
+        Running,
+        Released
+    };
+
     // Create an AudioContext for rendering to the audio hardware.
     static AudioContext* create(Document&, ExceptionState&);
 
@@ -95,6 +107,7 @@ public:
     size_t currentSampleFrame() const { return m_destinationNode->currentSampleFrame(); }
     double currentTime() const { return m_destinationNode->currentTime(); }
     float sampleRate() const { return m_destinationNode->sampleRate(); }
+    String state() const;
 
     AudioBuffer* createBuffer(unsigned numberOfChannels, size_t numberOfFrames, float sampleRate, ExceptionState&);
 
@@ -128,6 +141,10 @@ public:
     OscillatorNode* createOscillator();
     PeriodicWave* createPeriodicWave(Float32Array* real, Float32Array* imag, ExceptionState&);
 
+    // Pause/Resume
+    void suspendContext(ExceptionState&);
+    ScriptPromise resumeContext(ScriptState*);
+
     // When a source node has no more processing to do (has finished playing), then it tells the context to dereference it.
     void notifyNodeFinishedProcessing(AudioNode*);
 
@@ -274,6 +291,22 @@ private:
     // AudioNode::breakConnection() when we remove an AudioNode from this.
     HeapVector<Member<AudioNode> > m_referencedNodes;
 
+    // Stop rendering the audio graph.
+    void stopRendering();
+
+    // Handle Promises for resume().
+    void resolvePromisesForResume();
+    void resolvePromisesForResumeOnMainThread();
+
+    // Vector of promises created by resume(). It takes time to handle them, so we collect all of
+    // the promises here until they can be resolved or rejected.
+    Vector<RefPtr<ScriptPromiseResolver> > m_resumePromises;
+
+    // True if we're in the process of resolving promises for resume().  Resolving can take some
+    // time and the audio context process loop is very fast, so we don't want to call resolve an
+    // excessive number of times.
+    bool m_isResolvingResumePromises;
+
     class AudioNodeDisposer {
     public:
         explicit AudioNodeDisposer(AudioNode& node) : m_node(node) { }
@@ -338,6 +371,9 @@ private:
 
     bool m_isOfflineContext;
 
+    AudioContextState m_contextState;
+    void setContextState(AudioContextState);
+
     AsyncAudioDecoder m_audioDecoder;
 
     // Collection of nodes where the channel count mode has changed. We want the channel count mode