Convert blink_gc_plugin_flags.sh to a Python script.

Convert blink_gc_plugin_flags.sh to a Python script.

The motivation is being able to use it on Windows.

No intended behavior change.

https://codereview.chromium.org/1135853003/ will change blink
to call the new file, then the .sh forwarding script can go away.

BUG=467287
TBR=hans

Committed: https://chromium.googlesource.com/chromium/src/+/f7cd57c07ed0d874c7bab225e53303f7a5b7bb6a

[Nico, 2015-05-08 23:52:06]

thakis@chromium.org changed reviewers:
+ hans@chromium.org

[Nico, 2015-05-09 04:52:42]

The CQ bit was checked by thakis@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-05-09 04:56:29]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1137873002/40001

[commit-bot: I haz the power, 2015-05-09 12:15:47]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-05-09 12:15:49]

Dry run: Try jobs failed on following builders:
  android_chromium_gn_compile_dbg on tryserver.chromium.linux (JOB_TIMED_OUT, no
build URL)
  android_chromium_gn_compile_rel on tryserver.chromium.linux (JOB_TIMED_OUT, no
build URL)
  cast_shell_android on tryserver.chromium.linux (JOB_TIMED_OUT, no build URL)
  cast_shell_linux on tryserver.chromium.linux (JOB_TIMED_OUT, no build URL)
  chromium_presubmit on tryserver.chromium.linux (JOB_TIMED_OUT, no build URL)
  linux_chromium_asan_rel_ng on tryserver.chromium.linux (JOB_TIMED_OUT, no
build URL)
  linux_chromium_chromeos_compile_dbg_ng on tryserver.chromium.linux
(JOB_TIMED_OUT, no build URL)
  linux_chromium_chromeos_ozone_rel_ng on tryserver.chromium.linux
(JOB_TIMED_OUT, no build URL)
  linux_chromium_clobber_rel_ng on tryserver.chromium.linux (JOB_TIMED_OUT, no
build URL)
  linux_chromium_gn_chromeos_rel on tryserver.chromium.linux (JOB_TIMED_OUT, no
build URL)
  linux_chromium_gn_dbg on tryserver.chromium.linux (JOB_TIMED_OUT, no build
URL)
  linux_chromium_gn_rel on tryserver.chromium.linux (JOB_TIMED_OUT, no build
URL)
  linux_chromium_rel_ng on tryserver.chromium.linux (JOB_TIMED_OUT, no build
URL)

[Nico, 2015-05-09 19:59:16]

I'm going to TBR this so I can get the blink part in, so that that's hopefully
rolled into chromium by monday. Please do take a look, I will address all
comments. (Almost all comments won't require a 3-way-roll, so this is very
likely a huge latency win.)

I checked that flags are the same with and without this change on OS X. (I had a
few bugs, see diff from patch set 3 to 4, but it seems to be fine now.)

[Nico, 2015-05-09 19:59:32]

The CQ bit was checked by thakis@chromium.org

[commit-bot: I haz the power, 2015-05-09 20:00:17]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1137873002/60001

[commit-bot: I haz the power, 2015-05-09 20:19:38]

Patchset 4 (id:??) landed as
https://crrev.com/f7cd57c07ed0d874c7bab225e53303f7a5b7bb6a
Cr-Commit-Position: refs/heads/master@{#329054}

[Nico, 2015-05-09 20:20:21]

Committed patchset #4 (id:60001) manually as
f7cd57c07ed0d874c7bab225e53303f7a5b7bb6a (presubmit successful).

[hans, 2015-05-11 17:42:25]

lgtm