[Runtime] Add user href attribute check in widget element handler.

When parsing a widget config.xml file, runtime should make sure the author href
attribute is a valid URI, as it's required in W3C Widget spec. This patch will
fix this.

BUG=XWALK-2995
Unexpected crash when run/debug xwalkdriver unit tests

Add code to check the conditions of empty App icon. Since the runtime::app_icon() will
return an empty icon for Android non-host-application.

BUG=https://crosswalk-project.org/jira/browse/XWALK-2914
Merge pull request #2636 from iKevinHan/devtools_cause_crash_android

[Android] Fix devtools favicon will cause crash.
Merge pull request #2639 from takethathe/XWALK-2995

[Runtime] Add author href attribute check in widget element handler.
Bump version to 11.39.261.0