Fix unit tests for csp handler

This patch is changing the way in which manifest
and application objects are created.
All below tests now pass:
 - CSPHandlerTest.WGTCSP
 - CSPHandlerTest.WGTEmptyCSP
[Android] Use the same UserAgent for URLRequest when connection via websocket

Applying upstream commit 145b29d in content shell to crosswalk.

BUG=https://crosswalk-project.org/jira/browse/XWALK-3073
Merge pull request #2708 from wang16/ws_user_agent

[Android] Use the same UserAgent for URLRequest when connection via webs...
Merge pull request #2704 from aszafranek/CspHandlerTestFix

Fix unit tests for csp handler
[Application] Add the initialization for |header_|.

This patch is to add the initialization for |header_| in the
constructor.

CID=194686

Related to XWALK-2928.