[Android] Clear FLAG_FORCE_NOT_FULLSCREEN when entering fullscreen

The FLAG_FORCE_NOT_FULLSCREEN flag of Android Window will force the
Android system to show status bar, even with SYSTEM_UI_FLAG_FULLSCREEN
set in SystemUIVisibility.

Record whether the FLAG_FORCE_NOT_FULLSCREEN is set before entering
fullscreen and clear it if so. Add the flag back if necessary when
exiting fullscreen.

BUG=https://crosswalk-project.org/jira/browse/XWALK-2150
[Android] Add test case for onReceivedErrorTest().

This patch is to add test case for onReceivedErrorTest().
Open some urls with error format, the resource client will receive
the related error. Verify the error information with the expected
result.
Merge pull request #2220 from wang16/full_screen

[Android] Clear FLAG_FORCE_NOT_FULLSCREEN when entering fullscreen
Merge pull request #2212 from wuhengzhi/onReceivedLoadError_test

[Android] Add test case for onReceivedErrorTest().
[Android] Support 'xwalk_description' field in manifest.

Support 'xwalk_description' field in manifest according to W3C manifest spec.
The legacy field 'description' are still supported, but will print a warning message.