Remove unused IPC_MESSAGE_START enum constants.

ipc/ipc_message_start.h

Index: ipc/ipc_message_start.h
diff --git a/ipc/ipc_message_start.h b/ipc/ipc_message_start.h
index 091b12655a850f2ea79ab2f2c74d348e22ac772b..2d722438a128446678802c6d88e06c4fc46e00eb 100644
--- a/ipc/ipc_message_start.h
+++ b/ipc/ipc_message_start.h
@@ -30,7 +30,6 @@ enum IPCMessageStart {
   DatabaseMsgStart,
   DOMStorageMsgStart,
   IndexedDBMsgStart,
-  PepperFileMsgStart,
   SpeechRecognitionMsgStart,
   PepperMsgStart,
   AutofillMsgStart,
@@ -61,7 +60,6 @@ enum IPCMessageStart {
   ChromeUtilityMsgStart,
   MediaStreamMsgStart,
   ChromeBenchmarkingMsgStart,
-  IntentsMsgStart,
   JavaBridgeMsgStart,
   GamepadMsgStart,
   ShellMsgStart,
@@ -69,9 +67,7 @@ enum IPCMessageStart {
   PrefetchMsgStart,
   PrerenderMsgStart,
   ChromotingMsgStart,
-  OldBrowserPluginMsgStart,
   BrowserPluginMsgStart,
-  HyphenatorMsgStart,
   AndroidWebViewMsgStart,
   MetroViewerMsgStart,
   CCMsgStart,
@@ -79,9 +75,7 @@ enum IPCMessageStart {
   TracingMsgStart,
   PeerConnectionTrackerMsgStart,
   VisitedLinkMsgStart,
-  OneClickSigninMsgStart,
   AppShimMsgStart,
-  ValidationMessageMsgStart,
   WebRtcLoggingMsgStart,
   TtsMsgStart,
   MemoryBenchmarkMsgStart,