[webapi][XWALK-522] Optimize the test cases for promises

Impacted tests(approved): new 1, update 3, delete 0
Unit test platform: [Android]
Unit test result summary: pass 4, fail 0, block 0
[usecase-webapi] Disable forward button and show history state
[usecase-webapi] Improve Page Visibility usecase

- add description of locking screen/unlocking screen

Impacted TCs num(approved): New 0, Update 1, Delete 0
Unit test Platform: [Andriod]
Test result summary: Pass 1, Fail 0, Blocked 0
[usecase-webapi] Improve CSP usecase

- Add notice in csp-none page

Impacted TCs num(approved): New 0, Update 1, Delete 0
Unit test Platform: [Andriod]
Test result summary: Pass 1, Fail 0, Blocked 0
Merge pull request #581 from JianfengXu/xujf/csp/update

[usecase-webapi] Improve CSP usecase
Merge pull request #551 from zhuyongyong/yongzhu/sessionHistory/begining

[usecase-webapi] Disable forward button and show history state
Merge pull request #530 from zhuyongyong/yongzhu/promise-optimize

[webapi][XWALK-522] Optimize the test cases for promises
Merge pull request #580 from zhangjingx/zhangjingx/misc/pagevisibility

[usecase-webapi] Improve Page Visibility usecase
[usecase-webapi] Improve Navigation Timing usecase

- Group the timing checkpoints in a div, add a a reload button.

Impacted TCs num(approved): New 0, Update 1, Delete 0
Unit test Platform: Tizen M0
Tizen test result summary: Pass 1, Fail 0, Blocked 0
Merge pull request #623 from xinliux/xinliux/usecase/navigationtiming-improve

[usecase-webapi] Improve Navigation Timing usecase