Fix //content/test:test_support under component builds.

Fix //content/test:test_support under component builds.

Previously, //content/test:test_support depended directly on *_sources
targets. In component builds, this caused the browser_tests and
content_browsertests binaries to include their own copies of content as
well as depend on libcontent.so. This caused browser_tests and
content_browsertests to crash on startup. This CL changes test_support
to depend on the targets that forward to //content in component builds
and introduces such targets for gpu and ppapi_plugin.

The test_support changes also exposed underspecified dependencies in
extensions/renderer/BUILD.gn and third_party/libjingle/BUILD.gn, and
incorrect generated file dependencies in content/browser/devtools; the
generated files depend on other non-generated files so have to be
directly included in //content/browser.

BUG=432959
Committed: https://crrev.com/d06e3fcfcc33e9e5a9f427e21a17054a981fc7b9
Cr-Commit-Position: refs/heads/master@{#327188}

[Sam McNally, 2015-04-27 07:34:39]

Patchset #1 (id:1) has been deleted

[Sam McNally, 2015-04-27 08:45:41]

Patchset #2 (id:40001) has been deleted

[Sam McNally, 2015-04-27 09:20:25]

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

[Dirk Pranke, 2015-04-27 19:37:05]

lgtm

[Sam McNally, 2015-04-27 23:47:01]

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

[Sam McNally, 2015-04-27 23:47:01]

+brettw for OWNERS.

[brettw, 2015-04-28 00:02:28]

Nice! LGTM

[Sam McNally, 2015-04-28 00:09:49]

The CQ bit was checked by sammc@chromium.org

[commit-bot: I haz the power, 2015-04-28 00:10:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1104973002/60001

[commit-bot: I haz the power, 2015-04-28 00:15:05]

Committed patchset #2 (id:60001)

[commit-bot: I haz the power, 2015-04-28 00:16:05]

Patchset 2 (id:??) landed as
https://crrev.com/d06e3fcfcc33e9e5a9f427e21a17054a981fc7b9
Cr-Commit-Position: refs/heads/master@{#327188}