Update coroutines helpers with StateMachineChecker (#2829)

buildSrc/plugins/src/main/groovy/org/jetbrains/kotlin/KonanTest.groovy

@@ -211,6 +211,44 @@ abstract class KonanTest extends JavaExec {
             |    abstract fun resumeWithException(exception: Throwable)
             |    abstract fun resume(value: T)
             |}
+            |class StateMachineCheckerClass {
+            |    private var counter = 0
+            |    var finished = false
+            |
+            |    var proceed: () -> Unit = {}
+            |
+            |    suspend fun suspendHere() = suspendCoroutine<Unit> { c ->
+            |        counter++
+            |        proceed = { c.resume(Unit) }
+            |    }
+            |
+            |    fun check(numberOfSuspensions: Int) {
+            |        for (i in 1..numberOfSuspensions) {
+            |            if (counter != i) error("Wrong state-machine generated: suspendHere called should be called exactly once in one state. Expected " + i + ", got " + counter)
+            |            proceed()
+            |        }
+            |        if (counter != numberOfSuspensions)
+            |            error("Wrong state-machine generated: suspendHere called should be called exactly once in one state. Expected " + numberOfSuspensions + ", got " + counter)
+            |        if (finished) error("Wrong state-machine generated: it is finished early")
+            |        proceed()
+            |        if (!finished) error("Wrong state-machine generated: it is not finished yet")
+            |    }
+            |}            
+            |val StateMachineChecker = StateMachineCheckerClass()
+            |object CheckStateMachineContinuation: ContinuationAdapter<Unit>() {
+            |    override val context: CoroutineContext
+            |        get() = EmptyCoroutineContext
+            |
+            |    override fun resume(value: Unit) {
+            |        StateMachineChecker.proceed = {
+            |            StateMachineChecker.finished = true
+            |        }
+            |    }
+            |
+            |    override fun resumeWithException(exception: Throwable) {
+            |        throw exception
+            |    }
+            |}
         """.stripMargin()
     }