Patch 3/3 to get WebScheduler via WebThread

Patch 3/3 to get WebScheduler via WebThread

Now that all blink threads have schedulers it makes sense to get
hold the corresponding WebScheduler via WebThread.  This patch
removes the old Platform::scheduler() support in chromium.

Patch 1: https://codereview.chromium.org/1088053003
Patch 2: https://codereview.chromium.org/1087203002

BUG=463143
Committed: https://crrev.com/ed162fc872a8fe93811edbcd6b2f452656e2a6cd
Cr-Commit-Position: refs/heads/master@{#325824}

[alex clarke (OOO till 29th), 2015-04-15 11:19:40]

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

[rmcilroy, 2015-04-16 12:54:13]

On 2015/04/15 15:13:41, alexclarke1 wrote:

lgtm once rebased, thanks!

[Sami, 2015-04-16 12:57:49]

(lgtm)++

[alex clarke (OOO till 29th), 2015-04-16 14:01:03]

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

[alex clarke (OOO till 29th), 2015-04-16 14:01:04]

jochen@chromium.org: Can I get an owners review please

[jochen (gone - plz use gerrit), 2015-04-16 14:41:59]

lgtm

[alex clarke (OOO till 29th), 2015-04-20 08:56:40]

The CQ bit was checked by alexclarke@chromium.org

[alex clarke (OOO till 29th), 2015-04-20 08:56:40]

The patchset sent to the CQ was uploaded after l-g-t-m from
skyostil@chromium.org, rmcilroy@chromium.org
Link to the patchset: https://codereview.chromium.org/1084173002/#ps40001
(title: "Rebased")

[commit-bot: I haz the power, 2015-04-20 08:57:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1084173002/40001

[commit-bot: I haz the power, 2015-04-20 10:16:16]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-04-20 10:17:03]

Patchset 3 (id:??) landed as
https://crrev.com/ed162fc872a8fe93811edbcd6b2f452656e2a6cd
Cr-Commit-Position: refs/heads/master@{#325824}