Exclude ppapi_tests dep when enable_plugins=0.

Exclude ppapi_tests dep when enable_plugins=0.

We shouldn't include the ppapi_tests dependency when enable_plugins=0 is true.
In fact, we should probably get rid of most of the ppapi dependencies in that
case, but this change fixes a regression on one of the builders.

BUG=379018
R=dmichael@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=273862

[dmichael (off chromium), 2014-05-30 15:15:23]

lgtm

[teravest, 2014-05-30 15:15:48]

The CQ bit was checked by teravest@chromium.org

[commit-bot: I haz the power, 2014-05-30 15:16:52]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/teravest@chromium.org/308703004/1

[commit-bot: I haz the power, 2014-05-30 16:35:58]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  win_chromium_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/win_chromium_rel/buil...)
  win_gpu_triggered_tests on tryserver.chromium.gpu
(http://build.chromium.org/p/tryserver.chromium.gpu/builders/win_gpu_triggered...)

[commit-bot: I haz the power, 2014-05-30 16:38:50]

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

[commit-bot: I haz the power, 2014-05-30 16:38:52]

Try jobs failed on following builders:
  win_gpu_triggered_tests on tryserver.chromium.gpu
(http://build.chromium.org/p/tryserver.chromium.gpu/builders/win_gpu_triggered...)

[teravest, 2014-05-30 17:09:20]

Committed patchset #1 manually as r273862 (presubmit successful).