Implement web speech synthesis.

chrome/renderer/chrome_content_renderer_client.cc

Index: chrome/renderer/chrome_content_renderer_client.cc
diff --git a/chrome/renderer/chrome_content_renderer_client.cc b/chrome/renderer/chrome_content_renderer_client.cc
index 87d01c420d10fb97cd4f10cd79f1b29bbfc41c85..ffa05db05cf219cee0df37328af4c4970e483c63 100644
--- a/chrome/renderer/chrome_content_renderer_client.cc
+++ b/chrome/renderer/chrome_content_renderer_client.cc
@@ -70,6 +70,7 @@
 #include "chrome/renderer/searchbox/searchbox_extension.h"
 #include "chrome/renderer/spellchecker/spellcheck.h"
 #include "chrome/renderer/spellchecker/spellcheck_provider.h"
+#include "chrome/renderer/tts_dispatcher.h"
 #include "chrome/renderer/validation_message_agent.h"
 #include "components/autofill/renderer/autofill_agent.h"
 #include "components/autofill/renderer/password_autofill_agent.h"
@@ -1154,6 +1155,12 @@ void ChromeContentRendererClient::RegisterPPAPIInterfaceFactories(
 #endif
 }
 
+WebKit::WebSpeechSynthesizer*
+ChromeContentRendererClient::OverrideSpeechSynthesizer(
+    WebKit::WebSpeechSynthesizerClient* client) {
+  return new TtsDispatcher(client);
+}
+
 bool ChromeContentRendererClient::AllowBrowserPlugin(
     WebKit::WebPluginContainer* container) const {
   if (CommandLine::ForCurrentProcess()->HasSwitch(