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

chrome/renderer/chrome_render_view_observer.cc

Index: chrome/renderer/chrome_render_view_observer.cc
diff --git a/chrome/renderer/chrome_render_view_observer.cc b/chrome/renderer/chrome_render_view_observer.cc
index f3603e7b181fb26c964c5ff514c2dd867b164b2e..13b176a0df36b43a5b94308760d22175b5e1b1f9 100644
--- a/chrome/renderer/chrome_render_view_observer.cc
+++ b/chrome/renderer/chrome_render_view_observer.cc
@@ -51,6 +51,10 @@
 #include "ui/gfx/skbitmap_operations.h"
 #include "v8/include/v8-testing.h"
 
+#if defined(ENABLE_EXTENSIONS)
+#include "chrome/common/extensions/chrome_extension_messages.h"
+#endif
+
 using blink::WebAXObject;
 using blink::WebCString;
 using blink::WebDataSource;