Set extension-related webkit preferences in a common location.

Before we were ending up with different preferences set in
different locations.

I'm not sure if this approach is right from the content-team's
point of view.

BUG=
TEST=

Review URL: http://codereview.chromium.org/8403024

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@107882 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/chrome/chrome_browser.gypi b/chrome/chrome_browser.gypi
index ec8ed64..403699d 100644
--- a/chrome/chrome_browser.gypi
+++ b/chrome/chrome_browser.gypi
@@ -1197,6 +1197,8 @@
         'browser/extensions/extension_web_socket_proxy_private_api.h',
         'browser/extensions/extension_web_ui.cc',
         'browser/extensions/extension_web_ui.h',
+        'browser/extensions/extension_webkit_preferences.cc',
+        'browser/extensions/extension_webkit_preferences.h',
         'browser/extensions/extension_webnavigation_api.cc',
         'browser/extensions/extension_webnavigation_api.h',
         'browser/extensions/extension_webnavigation_api_constants.cc',