Resolve merge conflicts and update unit tests to match 3-state machine

Author: AgraVator

servlet/src/main/java/io/grpc/servlet/AsyncServletOutputStreamWriter.java

@@ -251,7 +251,18 @@ private void runOrBuffer(ActionItem actionItem) throws IOException {
           try {
             while (true) {
               if (itemToWrite != null) {
-                itemToWrite.run();
+                try {
+                  itemToWrite.run();
+                } catch (IllegalStateException e) {
+                  if (itemToWrite == flushAction || itemToWrite == completeAction) {
+                    throw e;
+                  }
+                  writeChain.offer(itemToWrite);
+                  writeState.set(new WriteState(WriteState.NOT_READY_OR_NOT_DRAINED));
+                  LockSupport.unpark(parkingThread);
+                  successfulExited = true;
+                  return;
+                }
                 if (itemToWrite == completeAction) {
                   writeState.set(new WriteState(WriteState.NOT_READY_OR_NOT_DRAINED));
                   LockSupport.unpark(parkingThread);

servlet/src/test/java/io/grpc/servlet/AsyncServletOutputStreamWriterTest.java

@@ -287,10 +287,11 @@ private static void forceReadyAndDrained(AsyncServletOutputStreamWriter writer)
     AtomicReference<Object> writeState =
         (AtomicReference<Object>) writeStateField.get(writer);
     Object curState = writeState.get();
-    Method withReadyAndDrained = curState.getClass().getDeclaredMethod(
-        "withReadyAndDrained", boolean.class);
-    withReadyAndDrained.setAccessible(true);
-    writeState.set(withReadyAndDrained.invoke(curState, true));
+    java.lang.reflect.Constructor<?> constructor =
+        curState.getClass().getDeclaredConstructor(int.class);
+    constructor.setAccessible(true);
+    Object newState = constructor.newInstance(0 /* READY_AND_DRAINED */);
+    writeState.set(newState);
   }
 
   @Test