Automatically trigger installation of high-quality speech synthesis extension.

chrome/common/extensions/extension_constants.h

Index: chrome/common/extensions/extension_constants.h
diff --git a/chrome/common/extensions/extension_constants.h b/chrome/common/extensions/extension_constants.h
index 50920e8e35b11e82d8ccf8b7fc6b3ccb65d859f7..c26d13309ab0055de7e721afdfeccbbb0bab0e0a 100644
--- a/chrome/common/extensions/extension_constants.h
+++ b/chrome/common/extensions/extension_constants.h
@@ -253,6 +253,9 @@ namespace extension_misc {
   extern const char kSpeechSynthesisExtensionPath[];
   // The extension id of the speech synthesis extension.
   extern const char kSpeechSynthesisExtensionId[];
+  // The extension id of the high quality speech synthesis extension for
+  // en-US, which can be installed automatically from the web store.
+  extern const char kHighQuality_en_US_ExtensionId[];
   // The extension id of the wallpaper manager application.
   extern const char kWallpaperManagerId[];
   // The extension id of the first run dialog application.