Roll GN binaries to #317120 for the cpu_arch changes

Roll GN binaries to #317120 for the cpu_arch changes

The newest version of GN replaces the 'cpu_arch' and 'os' variables with 'current_cpu', 'target_cpu', 'current_os', and 'target_os', and also replaces 'build_cpu' with 'host_cpu', and 'build_os' with 'host_os'.

The roll also picks up the change to add a new 'gn clean'
command, some absolute path handling fixes, a check_includes fix for action_foreach(), and some minor
internal fixes.

This patch also updates the build config files to accommodate the GN changes in a backwards-compatible manner, i.e., the configs now will set cpu_arch and os correctly in the right contexts. They will also allow the users to continue to set os= and cpu_arch= in an args file, so no user builds (or bots) will break.

Once all of the bots and all of the build files have been updated to refer to the new variables instead of the old ones, we can drop the backwards-compatible versions.

TBR=brettw@chromium.org
BUG=344767
CQ_EXTRA_TRYBOTS=tryserver.chromium.linux:android_chromium_gn_compile_dbg,android_chromium_gn_compile_rel;tryserver.chromium.win:win8_chromium_gn_rel,win8_chromium_gn_dbg;tryserver.chromium.mac:mac_chromium_gn_rel,mac_chromium_gn_dbg

Committed: https://crrev.com/7ee02bed35766535521c8e1f072b98cbf9eef53d
Cr-Commit-Position: refs/heads/master@{#317186}

[Dirk Pranke, 2015-02-19 00:15:08]

dpranke@chromium.org changed reviewers:
+ brettw@chromium.org

[Dirk Pranke, 2015-02-19 00:16:21]

Please take a look. This patch depends on the changes to GN in
https://codereview.chromium.org/914873002/ , and this CL needs to be updated to
include a GN roll once that patch has landed.

Once this patch lands, we can land subsequent CLs to update the build files and
the buildbots, and then remove the code.

[brettw, 2015-02-19 21:47:18]

lgtm

[Dirk Pranke, 2015-02-19 21:52:22]

New patchsets have been uploaded after l-g-t-m from brettw@chromium.org

[Dirk Pranke, 2015-02-19 22:03:19]

The CQ bit was checked by dpranke@chromium.org

[commit-bot: I haz the power, 2015-02-19 22:04:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/936103003/60001

[commit-bot: I haz the power, 2015-02-19 22:04:02]

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

[commit-bot: I haz the power, 2015-02-19 22:04:03]

Transient error: Invalid delimiter in
"android_chromium_gn_compile_dbg,android_chromium_gn_compile_rel,win8_chromium_gn_rel,win8_chromium_gn_dbg,mac_chromium_gn_rel,mac_chromium_gn_dbg":
Correct syntax is "tryserver:bot1,bot2;tryserver2:bot3,bot4;".

[Dirk Pranke, 2015-02-19 22:06:04]

The CQ bit was checked by dpranke@chromium.org

[commit-bot: I haz the power, 2015-02-19 22:07:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/936103003/60001

[commit-bot: I haz the power, 2015-02-19 22:14:56]

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

[commit-bot: I haz the power, 2015-02-19 22:14:57]

Try jobs failed on following builders:
  android_chromium_gn_compile_dbg on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/android_chromiu...)
  android_chromium_gn_compile_rel on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/android_chromiu...)

[Dirk Pranke, 2015-02-19 22:43:01]

The CQ bit was checked by dpranke@chromium.org

[commit-bot: I haz the power, 2015-02-19 22:43:49]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/936103003/80001

[commit-bot: I haz the power, 2015-02-20 00:16:27]

Committed patchset #5 (id:80001)

[commit-bot: I haz the power, 2015-02-20 00:17:08]

Patchset 5 (id:??) landed as
https://crrev.com/7ee02bed35766535521c8e1f072b98cbf9eef53d
Cr-Commit-Position: refs/heads/master@{#317186}