IDL compiler: Fix other re bugs in compute_dependencies.py

Today's fix re day!
Interface resolution wasn't working properly for
TestPartialInterfacePython2.idl
b/c the re was matching on a comment.
Making the re more explicit (trailing '\s*{') fixes this;
added to all interface re's for safety and consistency.

Followup to:
IDL compiler: Fix re in Perl IDL compiler
https://codereview.chromium.org/142703004/

BUG=239771
R=haraken

Review URL: https://codereview.chromium.org/143083002

git-svn-id: svn://svn.chromium.org/blink/trunk@165434 bbb929c8-8fbe-4397-9dbb-9b2b20218538