[Android] Implement the method of OnReceiveHttpAuthRequest() in runtime core
          and update the http authentication database interfaces.

1. Some web page has the requirement of http authentication, support
   this requirement by providing the method of OnReceiveHttpAuthRequest().
2. Update the http authentication database interfaces by removing the previous
   method of getInstance() and directly calling the constructor function
   of the class HttpAuthDatabase.

BUG=#788
Merge pull request #1021 from ShDavidliu/runtime_core

[Android] Implement the method of OnReceiveHttpAuthRequest().
[Runtime Model] Implement non-persistent main document.

The following CL is to implement
https://crosswalk-project.org/jira/browse/XWALK-2.

The CL makes ApplicationProcessManager as an Observer for Runtime
objects. Therefore, whenever a Runtime object/Window is added or
removed, the ApplicationProcessManager could be notified.