Pepper: More IDL generator cleanup.

Pepper: More IDL generator cleanup.

This change makes running the test for idl_c_proto work again, by fixing the
test.

It also removes an unused "BuiltIn" type list in idl_ast, which was very
confusing, and performs some other small cleanup I came across while adding
support for dev channel versions.

BUG=

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=238711

[bbudge, 2013-12-04 01:25:55]

Rubberstamp LGTM (I don't know this code very well.)

[commit-bot: I haz the power, 2013-12-04 01:55:42]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/teravest@chromium.org/98343005/40001

[commit-bot: I haz the power, 2013-12-04 02:25:18]

Retried try job too often on linux_rel for step(s) base_unittests,
browser_tests, cacheinvalidation_unittests, cc_unittests, check_deps,
chromedriver2_unittests, components_unittests, content_browsertests,
content_unittests, crypto_unittests, google_apis_unittests, gpu_unittests,
interactive_ui_tests, ipc_tests, jingle_unittests, media_unittests,
nacl_integration, net_unittests, ppapi_unittests, printing_unittests,
remoting_unittests, sandbox_linux_unittests, sql_unittests,
sync_integration_tests, sync_unit_tests, unit_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=linux_rel&...

[commit-bot: I haz the power, 2013-12-04 15:24:35]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/teravest@chromium.org/98343005/60001

[commit-bot: I haz the power, 2013-12-04 16:54:28]

Change committed as 238711