[Tizen] Add signature xsd file into crosswalk

Because crosswalk has replaced WRT in Tizen common image, some metadata
file which provided by wrt-installer package are missed.
signature_schema.xsd is used to verify whether signature.xml is valid.
[Tizen] Checking widget signature

Process signature file in widget according to
http://www.w3.org/TR/widgets-digsig/#signature-verification. Because
there is no Tizen CA root in image, reference validation and signature
validation on signature will be added when CA is ready.
[Android] Unregister broadcast receiver for notification properly

Unregister non-regsitered broadcast receiver will cause
crash on Android. The condition to detect whether the broadcast
receiver has been registered to receive Notification close
pending intent is change by commit eeeb8eeab.

BUG=https://crosswalk-project.org/jira/browse/XWALK-2356
Merge pull request #2291 from xuzhang/widgetsignatue

Widgetsignatue
GetUserAgent shouldn't have Mobile for IVI

Bug = XWALK-2317
Merge pull request #2326 from wang16/notification

[Android] Unregister broadcast receiver for notification properly
Roll blink crosswalk

- [Temp] Backport r178889 from upstream
Merge pull request #2327 from darktears/master

Roll blink crosswalk
Merge pull request #2322 from qjia7/alsa

Enable Alsa support
Merge pull request #2313 from qjia7/useragent

GetUserAgent shouldn't have Mobile for IVI
Revert "Enable Alsa support"
Merge pull request #2334 from crosswalk-project/revert-2322-alsa

Revert "Enable Alsa support"
Enable Alsa support

Bug=XWALK-2262