[Cast, Android, Presentation API] Check if mApiClient is connected or connecting before using it an…

[Cast, Android, Presentation API] Check if mApiClient is connected or connecting before using it anywhere.

Some of the messages are sent by the page while the stopApplication is being executed
and then mApiClient is null when we process the messages.

BUG=None

Committed: https://crrev.com/6bdc8b753d0ac7caec7f78ad7b558248ee0a3770
Cr-Commit-Position: refs/heads/master@{#356867}

[whywhat, 2015-10-29 13:59:01]

avayvod@chromium.org changed reviewers:
+ mlamouri@chromium.org

[whywhat, 2015-10-29 13:59:01]

PTaL

[mlamouri (slow - plz ping), 2015-10-29 15:34:06]

lgtm.

I think this might fix bug 544287. Can you check?

[whywhat, 2015-10-29 15:48:47]

The CQ bit was checked by avayvod@chromium.org

[commit-bot: I haz the power, 2015-10-29 15:49:59]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1410733008/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1410733008/1

[commit-bot: I haz the power, 2015-10-29 16:59:31]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-29 17:00:34]

Patchset 1 (id:??) landed as
https://crrev.com/6bdc8b753d0ac7caec7f78ad7b558248ee0a3770
Cr-Commit-Position: refs/heads/master@{#356867}