OOP PDF: Hide the loading indicator until the plugin loads.

OOP PDF: Hide the loading indicator until the plugin loads.

Previously if the PDF plugin is disabled or click-to-play, the loading
indicator appeared over the click-to-play overlay. This hides the
loading indicator until a message is received from the plugin.

BUG=441132
Committed: https://crrev.com/3d8aa0881d7de3b3ba8e3daea2478015cc429662
Cr-Commit-Position: refs/heads/master@{#308303}

[Sam McNally, 2014-12-12 02:55:39]

sammc@chromium.org changed reviewers:
+ raymes@chromium.org

[raymes, 2014-12-14 23:53:02]

lgtm

[Sam McNally, 2014-12-14 23:54:24]

The CQ bit was checked by sammc@chromium.org

[commit-bot: I haz the power, 2014-12-14 23:55:25]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/796223002/1

[commit-bot: I haz the power, 2014-12-15 00:52:27]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-12-15 00:53:09]

Patchset 1 (id:??) landed as
https://crrev.com/3d8aa0881d7de3b3ba8e3daea2478015cc429662
Cr-Commit-Position: refs/heads/master@{#308303}