Make an IdlCompiler class

Refactoring CL, inspired by and preliminary to Terry's "speed up r-b-t" CL.
This adds a thin wrapper class, IdlCompiler, which has two methods:
* Initialization (both IdlReader and CodeGeneratorV8)
* .compile()

The resulting main() is v. simple (clear initialization/compile);
this will also make Terry's CL considerably simpler and easier to review,
since he can just instantiate this class in r-b-t and call it repeatedly.

Terry's:
Faster PYTHON IDL dependency computation and parsing.
https://codereview.chromium.org/169743005/

R=haraken

Review URL: https://codereview.chromium.org/178003010

git-svn-id: svn://svn.chromium.org/blink/trunk@168340 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Clean up generated_bindings.gyp

This does some cleanup to GYP;
only change to build is consolidating two identical gyp-time files into one.

* Move temporary list file variables to the top, with other variables
  (keeps all these lists together, removes duplicate variables, and removes
   duplicate comments)
* Add comment lines between actions (GYP files are hard to read,
  and we're going to add more actions for caching lexer/parser)
* Fix indentation so consistent
(.gyp file formatting isn't terribly consistent or linted,
but this makes reading and edits easier)

BUG=341748
R=haraken

Review URL: https://codereview.chromium.org/181063013

git-svn-id: svn://svn.chromium.org/blink/trunk@168341 bbb929c8-8fbe-4397-9dbb-9b2b20218538