I am debugging with Android Studio (A.S) 1.0.2 with compileSdkVersion 21 set up in build.gradle. When using an emulator with API 21 everything works fine. The problem occurs
Open your project in Intellij Idea (Android Studio based on it) and choose File -> Project Structure.... In project setting select "project SDK" to version which you need debug and select for all project modules "project SDK" as module SDK. After that you can attach debug connection to your device/emulator and see proper Android source.
You don't need to build project in Intellij Idea.