[Extensions] Check validation of XWalkExtensionInstance before binding callbacks.

There is race condition that sometimes CreateInstance() return invalid
XWalkExtensionInstance.

So far, this crash does not happen on any C++ extensions or Android
extension tests. Only happens on CordovaTests apk. And worse and worse
when loadUrl calling times increased.

Meanwhile, the Android speicific function RegisterExtension() and
UnregisterExtension() are removed from xwalk_browser_main_parts.h

BUG=https://crosswalk-project.org/jira/browse/XWALK-1688
[Runtime] Disable extensions api for external web page.

We should only enable extension js api for frame which with
app scheme or file scheme.

BUG=XWALK-2153
Merge pull request #2221 from CooderIan/disable_api

[Runtime] Disable extensions api for external web page.
Move to M37.0.2062.20

- Skip SIMD command line for now.
- sync gyp_xwalk with gyp_chromium (r274762).
- Fixed the code for the Geolocation. Just like in M36 the delegate
has been refactored. It's now not a separate class to inherit from
but a regular object to instanciate. On other platforms than Tizen and Android
we need to make sure we return with the callback otherwise it hangs waiting for a reply.
As we do not support this on desktop we can just early return false.
- Fix 'screen' property not being replaced in a test : Blink commit 5fdac279
made the 'screen' property non-replaceable, so the only way to overwrite it
now is using v8tools utility to force.
- [Android] Strings now are generated differently through a dedicated GYP target.
- DEPS.xwalk: Start tracking Ozone-Wayland's Milestone-Summer branch.
- [Android] Fix resource packaging : In upstream the resource processing changed a
lot.
-[Tizen] Temporarily disable ALSA support : https://codereview.chromium.org/264973012 introduces a dependency on
ALSA's sequencing interface, which is currently disabled on Tizen.
- [Tizen] Add a patch for angle specific to Tizen to skip the .git/index dependency wrongly added. Fixed upstream
already http://code.google.com/p/chromium/issues/detail?id=395705
[Tizen] Temporarily disable WebRTC support (XWALK-2160)
Merge pull request #2228 from darktears/land-m37

Move to M37.0.2062.20
Increase Chromium version to 37.
Merge pull request #2222 from halton/validate_instance

[Extensions] Check validation of XWalkExtensionInstance before binding callbacks
[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.