scheduler: Add a base directory

scheduler: Add a base directory

This patch moves the more fundamental scheduling primitives (e.g.,
TaskQueueManager) to a separate base/ directory. This makes the layered
architecture of the scheduler more obvious and reduces the likelihood of
accidentally introducing layering violations.

With this refactoring, the overall dependencies are:

       +------+
       | base |
       +------+
           ^
           |
       +-------+     +------+
       | child |<----| test |
       +-------+     +------+
          ^ ^          ^ ^
          | |          | |
          | '----------|-|---.
          | .----------' '-. |
          | |              | |
      +----------+      +-------+
      | renderer |      | ppapi |
      +----------+      +-------+

Committed: https://crrev.com/516bee16e9437521cdd20a78d683f9dbaf35df3e
Cr-Commit-Position: refs/heads/master@{#351109}

Committed: https://crrev.com/0bbc9d23397f6c353186e86f34220f3f13e982b5
Cr-Commit-Position: refs/heads/master@{#351299}

[Sami, 2015-09-28 13:04:47]

skyostil@chromium.org changed reviewers:
+ alexclarke@chromium.org

[alex clarke (OOO till 29th), 2015-09-28 13:24:07]

lgtm

[Sami, 2015-09-28 14:23:42]

skyostil@chromium.org changed reviewers:
+ jochen@chromium.org

[Sami, 2015-09-28 14:24:43]

Thanks, +jochen@ for components/BUILD.gn (and anything in general that seems off
about this patch).

[jochen (gone - plz use gerrit), 2015-09-28 15:58:06]

lgtm

[Sami, 2015-09-28 16:00:29]

The CQ bit was checked by skyostil@chromium.org

[Sami, 2015-09-28 16:00:29]

The patchset sent to the CQ was uploaded after l-g-t-m from
alexclarke@chromium.org
Link to the patchset: https://codereview.chromium.org/1374653003/#ps60001
(title: "Missed one header guard.")

[commit-bot: I haz the power, 2015-09-28 16:02:25]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1374653003/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1374653003/60001

[commit-bot: I haz the power, 2015-09-28 18:06:58]

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

[commit-bot: I haz the power, 2015-09-28 18:06:59]

Try jobs failed on following builders:
  linux_android_rel_ng on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_android_r...)

[Sami, 2015-09-28 18:08:32]

The CQ bit was checked by skyostil@chromium.org

[commit-bot: I haz the power, 2015-09-28 18:10:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1374653003/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1374653003/60001

[commit-bot: I haz the power, 2015-09-28 19:27:59]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2015-09-28 19:29:24]

Patchset 4 (id:??) landed as
https://crrev.com/516bee16e9437521cdd20a78d683f9dbaf35df3e
Cr-Commit-Position: refs/heads/master@{#351109}

[pavely, 2015-09-28 22:10:53]

A revert of this CL (patchset #4 id:60001) has been created in
https://codereview.chromium.org/1370343002/ by pavely@chromium.org.

The reason for reverting is: Change causes compile failure:
http://build.chromium.org/p/chromium.linux/builders/Linux%20GN%20Clobber/buil...
.

[Sami, 2015-09-29 10:50:26]

The CQ bit was checked by skyostil@chromium.org

[Sami, 2015-09-29 10:50:27]

The patchset sent to the CQ was uploaded after l-g-t-m from jochen@chromium.org,
alexclarke@chromium.org
Link to the patchset: https://codereview.chromium.org/1374653003/#ps80001
(title: "Fixed gn clobber build.")

[commit-bot: I haz the power, 2015-09-29 10:50:59]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1374653003/80001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1374653003/80001

[commit-bot: I haz the power, 2015-09-29 12:28:15]

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

[commit-bot: I haz the power, 2015-09-29 12:28:16]

Try jobs failed on following builders:
  win_chromium_x64_rel_ng on tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_x64_...)

[Sami, 2015-09-29 12:29:43]

The CQ bit was checked by skyostil@chromium.org

[commit-bot: I haz the power, 2015-09-29 12:30:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1374653003/80001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1374653003/80001

[commit-bot: I haz the power, 2015-09-29 13:07:33]

Committed patchset #5 (id:80001)

[commit-bot: I haz the power, 2015-09-29 13:08:30]

Patchset 5 (id:??) landed as
https://crrev.com/0bbc9d23397f6c353186e86f34220f3f13e982b5
Cr-Commit-Position: refs/heads/master@{#351299}