Implement web speech synthesis.

content/public/browser/content_browser_client.h

Index: content/public/browser/content_browser_client.h
diff --git a/content/public/browser/content_browser_client.h b/content/public/browser/content_browser_client.h
index 5f8ffa3eeefd5428c7d8c9e5bb6aa2cae0a539f3..834907b9bb15323cd8a8c10d5945786defdeffdb 100644
--- a/content/public/browser/content_browser_client.h
+++ b/content/public/browser/content_browser_client.h
@@ -78,6 +78,7 @@ class RenderViewHostDelegateView;
 class ResourceContext;
 class SiteInstance;
 class SpeechRecognitionManagerDelegate;
+class TtsDispatcherHostDelegate;
 class WebContents;
 class WebContentsViewDelegate;
 class WebContentsViewPort;
@@ -424,6 +425,10 @@ class CONTENT_EXPORT ContentBrowserClient {
   virtual SpeechRecognitionManagerDelegate*
       GetSpeechRecognitionManagerDelegate();
 
+  // Allows the embedder to return a delegate for the TtsDispatcherHost.
+  // The delegate will be owned by the dispatcher. It's valid to return NULL.
+  virtual TtsDispatcherHostDelegate* GetTtsDispatcherHostDelegate();
+
   // Getters for common objects.
   virtual net::NetLog* GetNetLog();