IDL compiler: [ImplementedAs] on interface for attributes and methods

Followup to:
IDL compiler: [ImplementedAs] interfaces
https://codereview.chromium.org/103593002/

Need to add attributes and methods to test case, as affects configuration.

BUG=239771
NOTRY=true

Review URL: https://codereview.chromium.org/103843007

git-svn-id: svn://svn.chromium.org/blink/trunk@163516 bbb929c8-8fbe-4397-9dbb-9b2b20218538