chrome: Add ability to handle chrome menu/keyboard commands (fixes issue #3280)

This change adds a CefCommandHandler::OnChromeCommand callback for optionally
handling Chrome commands triggered via menus or keyboard shortcuts. Supported
command IDs are listed in a new cef_command_ids.h header file.

To test: Run `cefclient --enable-chrome-runtime --hide-controls`. Most commands
will blocked and removed from context menus.

tools/make_distrib.py

@@ -719,6 +719,7 @@ if mode == 'standard' or mode == 'minimal':
 
   # Transfer generated include files.
   generated_includes = [
+      'cef_command_ids.h',
       'cef_config.h',
       'cef_pack_resources.h',
       'cef_pack_strings.h',