[embedding][XWALK-2238] Add test cases to verify XWalkView.load()

 - Add test 2 cases for calling JS function with load and using XHR requests in XWalkView.
 - Update 1 case for calling JS function with evaluateJavascript.

Impacted tests(approved): new 2, update 1, delete 0
Unit test platform: [Android]
Unit test result summary: pass 3, fail 0, block 0