Update to Chromium revision 12bfc336 (#338390).

- The ffmpeg library is now statically linked (see https://codereview.chromium.org/1141703002).
- Off-screen rendering of the PDF viewer does not work in combination with surfaces. Pass the
  `--disable-surfaces` command-line flag if GPU is enabled (see https://codereview.chromium.org/1169983006).

libcef/browser/extensions/extension_system.h

@@ -86,6 +86,9 @@ class CefExtensionSystem : public ExtensionSystem {
     std::string extension_id;
   };
 
+  scoped_refptr<const Extension> CreateExtension(
+      const ComponentExtensionInfo& info, std::string* utf8_error);
+
   // Loads a registered component extension.
   const Extension* LoadExtension(const ComponentExtensionInfo& info);