Add browser_tests to the GN build.

Add browser_tests to the GN build.

Other misc fixes including:

Add "data_deps" to the templates in BUILDCONFIG. This was renamed from "datadeps" a while ago but both are still supported.

extension_management_test_util.cc includes a generated file policy_constants. GYP generates this with an extra "policy" directory but GN doesn't. The way GYP has the dirs set up, though, using only one "policy" works (and this is what other files do) so I just changed the include.

TBR=dpranke

Committed: https://crrev.com/7d6ec24650eb3f6c7ab8dcfcf0c2829095951962
Cr-Commit-Position: refs/heads/master@{#310276}

[brettw, 2015-01-07 12:49:28]

The CQ bit was checked by brettw@chromium.org

[commit-bot: I haz the power, 2015-01-07 12:50:08]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/824373003/60001

[commit-bot: I haz the power, 2015-01-07 13:01:19]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2015-01-07 13:02:11]

Patchset 4 (id:??) landed as
https://crrev.com/7d6ec24650eb3f6c7ab8dcfcf0c2829095951962
Cr-Commit-Position: refs/heads/master@{#310276}