Move extensions-only render IPC messages into the extension messages header.

chrome/renderer/content_settings_observer.cc

Index: chrome/renderer/content_settings_observer.cc
diff --git a/chrome/renderer/content_settings_observer.cc b/chrome/renderer/content_settings_observer.cc
index 5e3edbafeb8eef2713dfa13cc85c6bdf62a4bb66..4333ef86ff7949faa10b5ba75d07ccd9f1a0f28c 100644
--- a/chrome/renderer/content_settings_observer.cc
+++ b/chrome/renderer/content_settings_observer.cc
@@ -27,6 +27,10 @@
 #include "third_party/WebKit/public/web/WebView.h"
 #include "webkit/child/weburlresponse_extradata_impl.h"
 
+#if defined(ENABLE_EXTENSIONS)
+#include "chrome/common/extensions/chrome_extension_messages.h"
+#endif
+
 using blink::WebDataSource;
 using blink::WebDocument;
 using blink::WebFrame;