Split most extensions bits in ChromeRenderMessageFilter into ChromeExtensionMessageFilter.

chrome/chrome_browser.gypi

Index: chrome/chrome_browser.gypi
diff --git a/chrome/chrome_browser.gypi b/chrome/chrome_browser.gypi
index c0737cc1f236d0b8b3b2d0f09805d37820b7ea2c..9acb89504457d3b1d053c3edc77b2c7f14af6a98 100644
--- a/chrome/chrome_browser.gypi
+++ b/chrome/chrome_browser.gypi
@@ -1837,6 +1837,8 @@
         'browser/renderer_context_menu/spelling_bubble_model.h',
         'browser/renderer_context_menu/spelling_menu_observer.cc',
         'browser/renderer_context_menu/spelling_menu_observer.h',
+        'browser/renderer_host/chrome_extension_message_filter.cc',
+        'browser/renderer_host/chrome_extension_message_filter.h',
         'browser/renderer_host/chrome_render_message_filter.cc',
         'browser/renderer_host/chrome_render_message_filter.h',
         'browser/renderer_host/chrome_render_widget_host_view_mac_delegate.h',
@@ -2749,6 +2751,8 @@
             'browser/content_settings/content_settings_custom_extension_provider.h',
             'browser/content_settings/content_settings_internal_extension_provider.cc',
             'browser/content_settings/content_settings_internal_extension_provider.h',
+            'browser/renderer_host/chrome_extension_message_filter.cc',
+            'browser/renderer_host/chrome_extension_message_filter.h',
           ],
         }],
         ['enable_background==0', {