[iOS] Starting/stopping GCKDeviceScanner outside of main thread causes assertion

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Create an app that calls [GCKDeviceScanner startScan] on a background thread
2. Run the app

What is the expected output? What do you see instead?
The app crashes with the failure message below. If GCKDeviceScanner requires a 
certain thread, it should handle that internally rather than asserting.

*** Assertion failure in -[GCKDeviceScanner startScanInternal], 
/Volumes/BuildData/pulse-data/agents/wpyk11.hot/recipes/480401692/base/googlemac
/iPhone/Chromecast/SDKv2/Source/GCKDeviceScanner.m:118

What version of the product are you using? On what operating system?
Chromecast 17250
iOS 7.1

Please provide any additional information below.
N/A

Original issue reported on code.google.com by ten90jwhite@gmail.com on 27 Jun 2014 at 5:19

[GoogleCodeExporter]

I have a sample project the replicates the issue, but Google Code is not 
allowing me to attach it: "Project attachment quota exceeded."

Let me know who I can e-mail it to, if needed.

Original comment by ten90jwhite@gmail.com on 27 Jun 2014 at 5:25

[GoogleCodeExporter]

GCKDeviceScanner should be called from the main thread. Our documentation has 
been updated for both this method and GCKDeviceManager and will be reflected in 
the next release of iOS SDK to make this clear.

Original comment by anad...@google.com on 1 Aug 2014 at 10:49

• Changed state: WontFix