Revert of Removed the ScriptedSpeech content side.

content/public/common/content_switches.cc

Index: content/public/common/content_switches.cc
diff --git a/content/public/common/content_switches.cc b/content/public/common/content_switches.cc
index 81d584455ddc9a706c627f52cdc35ec3807217eb..c9d89d655179c3bdb232f6e7866961f08288041e 100644
--- a/content/public/common/content_switches.cc
+++ b/content/public/common/content_switches.cc
@@ -885,6 +885,9 @@
 // WebRTC is enabled by default on Android.
 const char kDisableWebRTC[]                 = "disable-webrtc";
 
+// Enable the recognition part of the Web Speech API.
+const char kEnableSpeechRecognition[]       = "enable-speech-recognition";
+
 // Always use the video overlay for the embedded video.
 // This switch is intended only for tests.
 const char kForceUseOverlayEmbeddedVideo[] = "force-use-overlay-embedded-video";