gn format //build

gn format //build

A starting point for doing all of src, and adding a PRESUBMIT.

Includes https://codereview.chromium.org/772663002/ and https://codereview.chromium.org/770053002/.
I haven't pushed new binaries yet.

Generated via:
> cd build
> git ls-files *.gn *.gni | sed -e "s/^/@..\\\\out\\\\Debug\\\\gn format --in-place /" >x.bat && x.bat

The only things that I don't love in the current output are:

1. Turning

    args = [
      "--depfile", rebase_path(depfile, root_build_dir),
      "--android-sdk-tools", rebased_android_sdk_build_tools,
      "--dex-path", rebased_output,
    ]

into:

    args = [
      "--depfile",
      rebase_path(depfile, root_build_dir),
      "--android-sdk-tools",
      rebased_android_sdk_build_tools,
      "--dex-path",
      rebased_output,
    ]

The heuristic for this isn't trivial though, and it also affects e.g. '-Xclang' in cflags, as well
as assignments to temporaries that are later assigned to args.

2. Turning single line

    if (defined(invoker.inputs)) { inputs = invoker.inputs }

into

    if (defined(invoker.inputs)) {
      inputs = invoker.inputs
    }

This could be argued to be an improvement, but as it's very boilerplate-y perhaps an exception to
allow single line in this case is worthwhile. I think there was discussion of new syntax for this
case too, something like "inputs ?= invoker.inputs" maybe.

In both cases, I think it's worthwhile to get formatting turned on, and then go back and special
case these if we decide it's worthwhile.

R=brettw@chromium.org
BUG=348474
Committed: https://crrev.com/b199254f481c5db36d56e83fce40594b06d2b81f
Cr-Commit-Position: refs/heads/master@{#306305}

[brettw, 2014-12-01 23:34:34]

lgtm sweet!

[scottmg, 2014-12-02 00:15:13]

The CQ bit was checked by scottmg@chromium.org

[commit-bot: I haz the power, 2014-12-02 00:16:32]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/766573003/60001

[commit-bot: I haz the power, 2014-12-02 00:25:30]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2014-12-02 00:26:05]

Patchset 4 (id:??) landed as
https://crrev.com/b199254f481c5db36d56e83fce40594b06d2b81f
Cr-Commit-Position: refs/heads/master@{#306305}

[tfarina, 2014-12-02 01:37:38]

I think 2 is wonderful! Reminds me Go (and I think it avoids bugs in the long
term). Cheers!