Add EmbedRoot to ViewManagerService.

Add EmbedRoot to ViewManagerService.

This means if you have an existing ViewManager connection you can just use that to ask the WM to embed a new node for you.

Also fix the issue where only one call to EmbedRoot() could be made to the init service prior to the window tree host being ready.

R=sky@chromium.org
BUG=none

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=284952

[sky, 2014-07-21 19:26:53]

LGTM if you rename Root to something else.

https://codereview.chromium.org/405163002/diff/20001/mojo/services/public/int...
File mojo/services/public/interfaces/view_manager/view_manager.mojom (right):

https://codereview.chromium.org/405163002/diff/20001/mojo/services/public/int...
mojo/services/public/interfaces/view_manager/view_manager.mojom:143:
EmbedRoot(string url) => (bool success);
Using 'root' here implies this gets the root, which is a bit confusing.

[Ben Goodger (Google), 2014-07-22 05:42:05]

The CQ bit was checked by ben@chromium.org

[commit-bot: I haz the power, 2014-07-22 05:43:30]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/ben@chromium.org/405163002/60001

[commit-bot: I haz the power, 2014-07-22 08:41:36]

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...)

[commit-bot: I haz the power, 2014-07-22 09:11:01]

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

[commit-bot: I haz the power, 2014-07-22 09:11:02]

Try jobs failed on following builders:
  win_chromium_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/win_chromium_rel/buil...)

[Ben Goodger (Google), 2014-07-23 16:45:09]

Committed patchset #4 manually as r284952 (presubmit successful).