Only release the result of a register request to a tab if it's still the foreground tab when the re…

chrome/browser/resources/cryptotoken/cryptotokenbackground.js

Index: chrome/browser/resources/cryptotoken/cryptotokenbackground.js
diff --git a/chrome/browser/resources/cryptotoken/cryptotokenbackground.js b/chrome/browser/resources/cryptotoken/cryptotokenbackground.js
index 800cdf8a16e654ab3500da95c89ccab5a135f0c1..e7ebcc71fb2550c376da2304e519599c12a1f0c2 100644
--- a/chrome/browser/resources/cryptotoken/cryptotokenbackground.js
+++ b/chrome/browser/resources/cryptotoken/cryptotokenbackground.js
@@ -37,6 +37,81 @@ var DEVICE_FACTORY_REGISTRY = new DeviceFactoryRegistry(
     new GoogleCorpIndividualAttestation());
 
 /**
+ * @param {*} request The received request
+ * @return {boolean} Whether the request is a register/enroll request.
+ */
+function isRegisterRequest(request) {
+  if (!request) {
+    return false;
+  }
+  switch (request.type) {
+    case GnubbyMsgTypes.ENROLL_WEB_REQUEST:
+      return true;
+
+    case MessageTypes.U2F_REGISTER_REQUEST:
+      return true;
+
+    default:
+      return false;
+  }
+}
+
+/**
+ * Default response callback to deliver a response to a request.
+ * @param {*} request The received request.
+ * @param {function(*): void} sendResponse A callback that delivers a response.
+ * @param {*} response The response to return.
+ */
+function defaultResponseCallback(request, sendResponse, response) {
+  response['requestId'] = request['requestId'];
+  try {
+    sendResponse(response);
+  } catch (e) {
+    console.warn(UTIL_fmt('caught: ' + e.message));
+  }
+}
+
+/**
+ * Response callback that delivers a response to a request only when the
+ * sender is a foreground tab.
+ * @param {*} request The received request.
+ * @param {!MessageSender} sender The message sender.
+ * @param {function(*): void} sendResponse A callback that delivers a response.
+ * @param {*} response The response to return.
+ */
+function sendResponseToActiveTabOnly(request, sender, sendResponse, response) {
+  tabInForeground(sender.tab.id).then(function(result) {
+    // If the tab is no longer in the foreground, drop the result: the user
+    // is no longer interacting with the tab that originated the request.
+    if (result) {
+      defaultResponseCallback(request, sendResponse, response);
+    }
+  });
+}
+
+/**
+ * Common handler for messages received from chrome.runtime.sendMessage and
+ * chrome.runtime.connect + postMessage.
+ * @param {*} request The received request
+ * @param {!MessageSender} sender The message sender
+ * @param {function(*): void} sendResponse A callback that delivers a response
+ * @return {Closeable} A Closeable request handler.
+ */
+function messageHandler(request, sender, sendResponse) {
+  var responseCallback;
+  if (isRegisterRequest(request)) {
+    responseCallback =
+        sendResponseToActiveTabOnly.bind(null, request, sender, sendResponse);
+  } else {
+    responseCallback =
+        defaultResponseCallback.bind(null, request, sendResponse);
+  }
+  var closeable = handleWebPageRequest(/** @type {Object} */(request),
+      sender, responseCallback);
+  return closeable;
+}
+
+/**
  * Listen to individual messages sent from (whitelisted) webpages via
  * chrome.runtime.sendMessage
  * @param {*} request The received request
@@ -48,28 +123,22 @@ function messageHandlerExternal(request, sender, sendResponse) {
   if (sender.id && sender.id === LOG_SAVER_EXTENSION_ID) {
     return handleLogSaverMessage(request);
   }
-  var closeable = handleWebPageRequest(/** @type {Object} */(request),
-      sender, function(response) {
-    response['requestId'] = request['requestId'];
-    try {
-      sendResponse(response);
-    } catch (e) {
-      console.warn(UTIL_fmt('caught: ' + e.message));
-    }
-  });
+
+  messageHandler(request, sender, sendResponse);
   return true;  // Tell Chrome not to destroy sendResponse yet
 }
 chrome.runtime.onMessageExternal.addListener(messageHandlerExternal);
 
 // Listen to direct connection events, and wire up a message handler on the port
 chrome.runtime.onConnectExternal.addListener(function(port) {
+  function sendResponse(response) {
+    port.postMessage(response);
+  }
+
   var closeable;
   port.onMessage.addListener(function(request) {
-    closeable = handleWebPageRequest(request, port.sender,
-        function(response) {
-          response['requestId'] = request['requestId'];
-          port.postMessage(response);
-        });
+    var sender = /** @type {!MessageSender} */ (port.sender);
+    closeable = messageHandler(request, sender, sendResponse);
   });
   port.onDisconnect.addListener(function() {
     if (closeable) {