[Android] Fix the failed test case about testPauseAndResume.

Due to the rebase to v32, the function "onActivityPause" and
"onActivityResume" was deleted from ContentViewCore.java.

The fix is to implement the onPause and onResume by another
function interfaces.

BUG=https://crosswalk-project.org/jira/browse/XWALK-351
Merge pull request #1150 from wuhengzhi/pauseResume

[Android] Fix the failed test case about testPauseAndResume.