Rename RootViewManager to DisplayManager

Rename RootViewManager to DisplayManager

DisplayManager is a better name for what the object is intended to do.

BUG=none
TEST=none
R=jamesr@chromium.org

Committed: https://crrev.com/344b4602f0495b0bd2fe370277ca2ab9ef59820f
Cr-Commit-Position: refs/heads/master@{#292077}

[jamesr, 2014-08-26 23:20:43]

lgtm

[sky, 2014-08-26 23:20:55]

The CQ bit was checked by sky@chromium.org

[commit-bot: I haz the power, 2014-08-26 23:21:37]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/sky@chromium.org/510483003/1

[commit-bot: I haz the power, 2014-08-27 01:19:19]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  linux_chromium_rel_swarming on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[commit-bot: I haz the power, 2014-08-27 02:01:02]

Committed patchset #1 (1) as 50e4edfb99a1ec643e6251f4e6d14db50a7f275a

[commit-bot: I haz the power, 2014-09-10 02:49:03]

Patchset 1 (id:??) landed as
https://crrev.com/344b4602f0495b0bd2fe370277ca2ab9ef59820f
Cr-Commit-Position: refs/heads/master@{#292077}