IInAppBillingService.java was created by running the following command:
$ANDROID_HOME/build-tools/34.0.0/aidl --lang=java \
-I$ANDROID_HOME/platforms/android-34/framework.aidl \
-Isrc/java \
-I. \
-o src/java \
src/java/com/android/vending/billing/IInAppBillingService.aidl