Fix up gles2 thunk targets a bit

Fix up gles2 thunk targets a bit

This puts the gles2 thunks target in a more reasonable location, stops abusing
static_library to hide dependency issues, and stop the view manager client side
library from pretending to know which sort of gles2 to link against. It uses
the gles2 headers but depending on whether the lib is being linked into an
application or linked into a target that links in the shell lib (as is done in
unit tests) it needs a different implementation. This also deletes the unused
//mojo/public/gles2/gles2_interface.h file - if we want this we can pull it
back but since nobody is using it now it's kind of a waste of space. If we do
want it, it should go in //mojo/public/cpp/gles2 since it's a C++ wrapper.

R=viettrungluu@chromium.org

Committed: https://crrev.com/8deb674e6cc3bf082bb9c05b6915f7a1d6db9c20
Cr-Commit-Position: refs/heads/master@{#297040}

[viettrungluu, 2014-09-26 15:41:35]

lgtm

[jamesr, 2014-09-26 18:29:31]

The CQ bit was checked by jamesr@chromium.org

[jamesr, 2014-09-26 18:30:06]

The CQ bit was unchecked by jamesr@chromium.org

[jamesr, 2014-09-26 19:35:34]

The CQ bit was checked by jamesr@chromium.org

[commit-bot: I haz the power, 2014-09-26 19:37:10]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/604223002/40001

[commit-bot: I haz the power, 2014-09-26 20:03:43]

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

[commit-bot: I haz the power, 2014-09-26 20:03:45]

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

[jamesr, 2014-09-26 20:17:52]

The CQ bit was checked by jamesr@chromium.org

[commit-bot: I haz the power, 2014-09-26 20:18:24]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/604223002/60001

[commit-bot: I haz the power, 2014-09-26 21:28:42]

Committed patchset #4 (id:60001) as 2a79e36e15727dd08172ca0285b55975992161b6

[commit-bot: I haz the power, 2014-09-26 21:29:15]

Patchset 4 (id:??) landed as
https://crrev.com/8deb674e6cc3bf082bb9c05b6915f7a1d6db9c20
Cr-Commit-Position: refs/heads/master@{#297040}