Port generate_gles2_conform_embedded_files action to GN build.

Port generate_gles2_conform_embedded_files action to GN build.

It requires internal test files, hence it was not tested.

Partially tested on Linux with the following command lines:

$ gn gen out-gn --args='internal_gles2_conform_tests'

BUG=432959
TEST=see above
R=dpranke@chromium.org,sievers@chromium.org

Committed: https://crrev.com/c0d45b8572d49861651342cb01fd85f956dc3309
Cr-Commit-Position: refs/heads/master@{#322639}

[Dirk Pranke, 2015-03-27 20:24:10]

lgtm

[no sievers, 2015-03-27 20:36:02]

lgtm

[tfarina, 2015-03-27 20:49:27]

The CQ bit was checked by tfarina@chromium.org

[commit-bot: I haz the power, 2015-03-27 20:49:44]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1041883002/1

[commit-bot: I haz the power, 2015-03-27 20:53:22]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-27 20:54:13]

Patchset 1 (id:??) landed as
https://crrev.com/c0d45b8572d49861651342cb01fd85f956dc3309
Cr-Commit-Position: refs/heads/master@{#322639}