[MR tests] Assert initial state / state change for reconnect case.

chrome/test/media_router/resources/common.js

Index: chrome/test/media_router/resources/common.js
diff --git a/chrome/test/media_router/resources/common.js b/chrome/test/media_router/resources/common.js
index 3f61ae4d1bdc5c49b87202f7b5458b748a55299c..d7f4241331d94367880232ccb047ccc163c92080 100644
--- a/chrome/test/media_router/resources/common.js
+++ b/chrome/test/media_router/resources/common.js
@@ -71,18 +71,7 @@ function checkSession() {
       } else {
         // set the new session
         startedConnection = session;
-        console.log('connection state is "' + startedConnection.state + '"');
-        if (startedConnection.state == "connected") {
-          sendResult(true, '');
-        } else if (startedConnection.state == "connecting") {
-          startedConnection.onconnect = () => {
-            sendResult(true, '');
-          };
-        } else {
-          sendResult(false,
-            'Expect connection state to be "connecting" or "connected", ' +
-            'actual "' + startedConnection.state + '"');
-        }
+        waitForConnectedStateAndSendResult(startedConnection);
       }
     }).catch(function(e) {
       // terminate old session if exists
@@ -93,6 +82,26 @@ function checkSession() {
 }
 
 /**
+ * Asserts the current state of the connection is 'connected' or 'connecting'.
+ * If the current state is connecting, waits for it to become 'connected'.
+ * @param {!PresentationConnection} connection
+ */
+function waitForConnectedStateAndSendResult(connection) {
+  console.log(`connection state is "${connection.state}"`);
+  if (connection.state == 'connected') {

[mark a. foltz, 2017/01/26 19:32:23]

When would this be 'connected'?  The state must be 'connecting' in the start()
Promise resolver.

https://w3c.github.io/presentation-api/#starting-a-presentation-connection

[takumif, 2017/01/26 21:28:29]

In checkSession() we're passing in a resolver function to |startSessionPromise|
which had previously been returned. So wouldn't it be possible for the
connection state to have changed to 'connected' before we pass in the resolver?

This is the browser test I was referring to in another CL [1] regarding this
issue, but now I think it's possible for the state to be 'connected' here,
unless I'm misunderstanding how promises work.

[1] https://codereview.chromium.org/2643473002/

[mark a. foltz, 2017/01/26 22:27:24]

Yes, if the Promise is already settled the connection could be in any state.

+    sendResult(true, '');
+  } else if (connection.state == 'connecting') {
+    connection.onconnect = () => {
+      sendResult(true, '');
+    };
+  } else {
+    sendResult(false,
+      `Expect connection state to be "connecting" or "connected", actual: \
+      "${connection.state}"`);
+  }
+}
+
+/**
  * Checks the start() request fails with expected error and message substring.
  * @param {!string} expectedErrorName
  * @param {!string} expectedErrorMessageSubstring
@@ -184,7 +193,7 @@ function reconnectSession(sessionId) {
       sendResult(false, 'reconnectSession returned null session');
     } else {
       reconnectedSession = session;
-      sendResult(true, '');
+      waitForConnectedStateAndSendResult(reconnectedSession);
     }
   }).catch(function(error) {
     sendResult(false, 'reconnectSession failed: ' + error.message);