Demo Crosswalk transparency bug

Demo test case for XWALK-3308.

This app has three flavors:

• withoutCrosswalk
• withCrosswalkArmv7
• withCrosswalkX86

To install the no-Crosswalk (i.e. WebView) version, do:

./gradlew installWithoutCrosswalkDebug

To install the Crosswalk version on an Armv7 device, do:

./gradlew installWithCrosswalkArmv7Debug