Add NetworkService support for chrome and chrome-devtools schemes (see issue #2622).

Known behavior changes:
- Unsupported chrome hosts no longer redirect to chrome://version.

To test: All tests pass with NetworkService disabled. WebUITest.* and V8Test.*
tests pass with NetworkService enabled.

libcef/browser/resource_context.h

@@ -88,6 +88,8 @@ class CefResourceContext : public content::ResourceContext {
   }
 
  private:
+  void InitOnIOThread();
+
   // Only accessed on the IO thread.
   bool is_off_the_record_;
   scoped_refptr<extensions::InfoMap> extension_info_map_;