Disable speech synthesis API for content/ layer.

android_webview/lib/main/aw_main_delegate.cc

Index: android_webview/lib/main/aw_main_delegate.cc
diff --git a/android_webview/lib/main/aw_main_delegate.cc b/android_webview/lib/main/aw_main_delegate.cc
index 8dd0648c27519aa8fc8ca52d835923128219c558..079a58506f903dc65c81610beb43598ecd892e69 100644
--- a/android_webview/lib/main/aw_main_delegate.cc
+++ b/android_webview/lib/main/aw_main_delegate.cc
@@ -78,6 +78,10 @@ bool AwMainDelegate::BasicStartupComplete(int* exit_code) {
 
   // WebRTC hardware decoding is not supported, internal bug 15075307
   cl->AppendSwitch(switches::kDisableWebRtcHWDecoding);
+
+  // Speech Synthesis backend resides in the chrome layer, not used by WebView.
+  // http://crbug.com/347045 tracks moving the backend to the content layer.
+  cl->AppendSwitch(switches::kDisableSpeechSynthesis);
   return false;
 }