Remove separate 'support' list of IDL files

Cleanup CL: no changes to generated bindings, just simplify code.

Background:
Separate 'support' lists of IDL files were added so that we could compute
dependencies for testing IDL files without affecting the actual generated
bindings.

This was done by Kihong back in:
Support partial interface for test support idls
https://codereview.chromium.org/24053003/

This complexity was necessary (thanks Kihong!) due to compute_bindings.py
being an inflexible mess, and just piled more complexity into GYP,
compute_bindings.py, and even run-bindings-tests (!).

For testing IDL files, we generate individual bindings, but we don't
put them in the aggregate generated bindings (b/c we don't want to ship them!)
and we don't put them on the global object (Window).

Now that I've cleaned up compute_bindings.py and the aggregate generated
bindings file generation, this distinction is no longer necessary, so
we can remove all this cruft.


Changes:
The only substantive change is that we now need to specify
[NoInterfaceObject] on IDL files for testing interfaces,
which should have been done all along: this prevents them from being put
on the global object, and makes this explicit.

Testing IDLs aren't in the aggregate bindings b/c we have a list just for
which IDL files to include there. I've written brief comments to explain
what each list of IDL files is for.

Testing-wise, this lets us remove a hack (merging two pickles!) and a layer
of nesting in run-bindings-tests.

The comment for why we have to compute real dependencies was a bit vague,
so I've made it more explicit.

This also lets us eliminate the separate testing/ IDL test files,
which were just there to exercise this 'support' list.

I've accordingly renamed various GYP variables to remove 'support'.

R=haraken
TBR=abarth

Review URL: https://codereview.chromium.org/134943004

git-svn-id: svn://svn.chromium.org/blink/trunk@165615 bbb929c8-8fbe-4397-9dbb-9b2b20218538