Revert of Move content_gl_tests.isolate to content.

Revert of Move content_gl_tests.isolate to content. (patchset #8 id:240001 of https://codereview.chromium.org/573073003/)

Reason for revert:
Failing bot in content_gl_tests, see 

http://build.chromium.org/p/chromium.gpu/builders/Win7%20Debug%20%28NVIDIA%29/builds/22782

Original issue's description:
> Move content_gl_tests.isolate to content.
> 
> I noticed this while looking through isolate files. Since the test target is in content, the isolate file should be alongside.
> 
> Committed: https://crrev.com/1351139b75882cf05417aa615df21d641870be3c
> Cr-Commit-Position: refs/heads/master@{#295983}

TBR=kbr@chromium.org,jam@chromium.org
NOTREECHECKS=true
NOTRY=true

[Jamie Madill, 2014-09-22 18:54:35]

Created Revert of Move content_gl_tests.isolate to content.

[commit-bot: I haz the power, 2014-09-22 18:55:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/590243002/1

[commit-bot: I haz the power, 2014-09-22 18:55:17]

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

[commit-bot: I haz the power, 2014-09-22 18:55:18]

No LGTM from a valid reviewer yet. Only full committers are accepted.
Even if an LGTM may have been provided, it was from a non-committer or
a provisional committer, _not_ a full super star committer.
See http://www.chromium.org/getting-involved/become-a-committer
Note that this has nothing to do with OWNERS files.

[Ken Russell (switch to Gerrit), 2014-09-22 19:17:32]

Since the original CL passed the commit queue it doesn't seem appropriate to
revert it. We'll figure out what's going on with the component builds on Windows
7. Closing this CL.