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 31cc72bdb4e4b28b16af6e15515f229403306426..b6dcc01c357980d477ee6b7b40dd782142415b61 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 "components/autofill/renderer/autofill_agent.h"
 #include "components/autofill/renderer/password_autofill_agent.h"
 #include "components/autofill/renderer/password_generation_manager.h"
@@ -1152,6 +1153,12 @@ 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(