Implement suspend() and resume() for OfflineAudioContext

Source/modules/webaudio/AudioNode.h

Index: Source/modules/webaudio/AudioNode.h
diff --git a/Source/modules/webaudio/AudioNode.h b/Source/modules/webaudio/AudioNode.h
index 1a7d57a70d0d0b146566622e74a0178a67bde359..c055ba833158ccb6c3d0eedd0cfbb0e614191928 100644
--- a/Source/modules/webaudio/AudioNode.h
+++ b/Source/modules/webaudio/AudioNode.h
@@ -107,7 +107,7 @@ public:
     // nullptr otherwise.  This always returns a valid object in an audio
     // rendering thread, and inside dispose().  We must not call context() in
     // the destructor.
-    AbstractAudioContext* context() const;
+    virtual AbstractAudioContext* context() const;
     void clearContext() { m_context = nullptr; }
 
     enum ChannelCountMode {
@@ -229,6 +229,12 @@ protected:
     // Force all inputs to take any channel interpretation changes into account.
     void updateChannelsForInputs();
 
+    // This raw pointer is safe because this is cleared for all of live
+    // AudioHandlers when the AbstractAudioContext dies.  Do not access m_context
+    // directly, use context() instead.
+    GC_PLUGIN_IGNORE("http://crbug.com/404527")
+    AbstractAudioContext* m_context;
+
 private:
     void setNodeType(NodeType);
 
@@ -241,12 +247,6 @@ private:
     GC_PLUGIN_IGNORE("http://crbug.com/404527")
     AudioNode* m_node;
 
-    // This raw pointer is safe because this is cleared for all of live
-    // AudioHandlers when the AbstractAudioContext dies.  Do not access m_context
-    // directly, use context() instead.
-    GC_PLUGIN_IGNORE("http://crbug.com/404527")
-    AbstractAudioContext* m_context;
-
     float m_sampleRate;
     Vector<OwnPtr<AudioNodeInput>> m_inputs;
     Vector<OwnPtr<AudioNodeOutput>> m_outputs;