Discard session after exception to clear up storage

Storage leaks can still happen if session commits have errors (for
instance, because the device was shutdown during installation), as those
sessions can still be reopened and retried according to docs. However,
we may expect all dangling sessions to be cleared after a certain
timespan in the magnitude of a day.

vending-app/src/main/kotlin/com/android/vending/installer/Install.kt

@@ -102,10 +102,10 @@ private suspend fun Context.installPackagesInternal(
     try {
         sessionId = packageInstaller.createSession(params)
         session = packageInstaller.openSession(sessionId)
-        componentNames.forEach { component ->
+        for (component in componentNames) {
             session.openWrite(component, 0, -1).use { outputStream ->
                 writeComponent(component, outputStream)
-                session.fsync(outputStream)
+                session!!.fsync(outputStream)
             }
         }
         val deferred = CompletableDeferred<Unit>()
@@ -127,13 +127,17 @@ private suspend fun Context.installPackagesInternal(
 
         emitProgress(CommitingSession)
         session.commit(pendingIntent.intentSender)
+        // don't abandon if `finally` step is reached after this point
+        session = null
 
         Log.d(TAG, "installPackages session commit")
         return deferred.await()
     } catch (e: IOException) {
         Log.w(TAG, "Error installing packages", e)
         throw e
     } finally {
-        session?.close()
+        Log.d(TAG, "Discarding session after error")
+        // discard downloaded data
+        session?.abandon()
     }
 }