Implement web speech synthesis.

Refactors TtsController a bit so that it can be used
both by Tts extensions and by web speech. Implements
almost all of the features of the web speech API.

Requires corresponding WebKit patch:
https://bugs.webkit.org/show_bug.cgi?id=111695

BUG=171887
NOTRY=true

Review URL: https://chromiumcodereview.appspot.com/12589005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@198060 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/content/public/renderer/content_renderer_client.cc b/content/public/renderer/content_renderer_client.cc
index 8997832..fe80e4d 100644
--- a/content/public/renderer/content_renderer_client.cc
+++ b/content/public/renderer/content_renderer_client.cc
@@ -75,6 +75,11 @@
   return NULL;
 }
 
+WebKit::WebSpeechSynthesizer* ContentRendererClient::OverrideSpeechSynthesizer(
+    WebKit::WebSpeechSynthesizerClient* client) {
+  return NULL;
+}
+
 bool ContentRendererClient::RunIdleHandlerWhenWidgetsHidden() {
   return true;
 }