[embedding][XWALK-1052] Leverage developer's sample tests for extension.

- Add extension support for embedding API.

Impacted tests(designed|approved): new 1, update 0, delete 0
Unit test platform: [Android]
Unit test result summary: pass 1, fail 0, block 0
[usecase-webapi] Fix the bug that the 'Pass' button is disabled when click the 'Cancle CSS FullScreen' button.

Impacted tests(approved): New 0, Update 1, Delete 0
Unit test platform: [TIZEN IVI]
Unit test result summary: Pass 1, Fail 0, Block 0
[webapi-usecase] Intergation of all subcases to one page for CSSStyleAttribute

- Fail Reason:[XWALK-1326]

Impacted TCs num: New 0, Update 1, Delete 0
Unit test Platform: [Andriod]
Unit test result summary: Pass 0, Fail 1, Blocked 0
[usecase-webapi] Add subcase in tests xml

- Add subcase attribute in <testcase>
- Remove redundant elements in tests xml

Impacted tests(approved): new 0, update 3, delete 0
Unit test platform: [Android]
Unit test result summary: pass 1, fail 2, block 0
[webapi][XWALK-2101] Add audio playback for audiosytem

- Fail Reason: Its not playing using pulseaudio by launching from xwalk-launcher.

Impacted TCs num(approved): New 0, Update 8, Delete 0
Unit test Platform: [Tizen IVI]
Unit test result summary: Pass 0, Fail 8, Blocked 0
[embedding][XWALK-1052] Add one line to import Method class

Impacted tests(approved): new 0, update 1, delete 0
Unit test platform: [Android]
Unit test result summary: pass 72, fail 17, block 4
[webapi][XWALK-2344] Update test step for gamepad

- To fire gamepadconnected event, need reconnect gamepad.

Impacted TCs num(approved): New 0, Update 3, Delete 0
Unit test Platform: Andriod
Unit test result summary: Pass 3, Fail 0, Blocked 0
[behavior] Update tests id due to folder renamed

- Update 2 tests id because test folder renamed
- Remove 1 designed test becasue test files have been removed
- Unify component name

Impacted tests(approved): new 0, update 2, delete 0
Unit test platform: [Tizen IVI]
Unit test result summary: pass 0, fail 2, block 0
Merge pull request #724 from haoxli/haoxli/behavior/fix-test-id

[behavior] Update tests id due to folder renamed
Merge pull request #721 from JianfengXu/xujf/2101

[webapi][XWALK-2101] Add audio playback for audiosytem
[webapi][XWALK-2334] Remove a pop-up during executing "CSS3BG_background-attach$

Impacted tests(approved): New 0, Update 1, Delete 0
Unit test platform: [Android]
Unit test result summary: Pass 1, Fail 0, Block 0
[webapi][XWALK-893] Update the key of iap

- Modify the key of iap app
- Failure analysis: The restore method does not suppot
- Block analysis: "In App Purchase" feature does not allowed in China

Impacted tests(approved): new 6, update 24, delete 0
Unit test platform: [Android]
Unit test result summary: pass 6, fail 2, block 22
Merge pull request #719 from haoxli/haoxli/webapi-usecase-w3c/add-subcase

[usecase-webapi] Add subcase in tests xml
Merge pull request #726 from yunxliu/yunxliu/webapi/update_iap_key

[webapi][XWALK-893] Update the key of iap
Merge pull request #722 from JianfengXu/xujf/2344

[webapi][XWALK-2344] Update test step for gamepad
Merge pull request #723 from minxhuang/hm/webapi/xwalk-2334-hotfix

[webapi][XWALK-2334] Remove pop-up for backgrounds
Merge pull request #714 from JianfengXu/xujf/style/update

[webapi-usecase] Intergation of all subcases to one page for CSSStyleAttribute
[webapi] Update the dir of 'How to build IAP extension'wiki

- Update the dir of 'How to build IAP extension'wiki
Merge pull request #727 from yunxliu/yunxliu/webapi/modify_iap

[webapi] Update the dir of 'How to build IAP extension'wiki
Merge pull request #720 from zhuyongyong/yongzhu/embeddingAPI/improve

[embedding][XWALK-1052] Add one line to import Method class