Adding API to allow async inflaiton of AppWidget

Test: Manual and unit tests
adb shell am instrument -e class android.widget.AppWidgetHostViewTest -w com.android.frameworks.coretests/android.support.test.runner.AndroidJUnitRunner

Bug: 22839968
Change-Id: Id9cb56619653f43b9f755c881f5d0936375f9c87
5 files changed