Files app: Fix test stepper with async load of test functions

After crrev.com/c/1322340 which changed test functions to be lazy
loaded (asynchronously), running tests in step-by-step mode wasn't
working if tried to step after Files app background page was put to
sleep for inactivity.

There were 2 issues:

1. The logic was relying on a global state window.IN_TEST which gets
lost when extension goes to sleep.

2 Any queued response was replied with sendResponse(true), which was
skipping the execution of the test function that it requested to run.

This CL fixes both of these issues by doing:

1. Instead of relying on window.IN_TEST, it checks if test functions
are loaded with: "test.util.executeTestMessage !== null", if so runs
the requested function, otherwise en-queues the request and async-loads
the test functions.

2. Change to en-queue both the request and the sendResponse to be able
to run the requested functions once the test functions are fully
loaded.

This new design, made |enableTesting| and |ensureLoaded_| routines not
necessary anymore and they were removed.

Test: Manually run tests with the flags: --ui-test-action-timeout=100000
--enable-file-manager-step-by-step-tests  --remote-debugging-port=9222
and waited all extensions to disappear before issuing a step. Also
triggered MSAN and ASAN bots in addition to normal bots.

Bug: 903669
Change-Id: Ia66f7ce7cd920a7a815340119591ff5ff957603c
Reviewed-on: https://chromium-review.googlesource.com/c/1333177
Commit-Queue: Luciano Pacheco <lucmult@chromium.org>
Reviewed-by: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607842}

ui/file_manager/file_manager/background/js/test_util_base.js

@@ -40,14 +40,10 @@ test.util.executeTestMessage = null;
  * Registers message listener, which runs test utility functions.
  */
 test.util.registerRemoteTestUtils = function() {
-  /**
-   * Responses that couldn't be sent while waiting for test scripts to load.
-   * Null if there is no load in progress.
-   * @type{Array<function(*)>}
-   */
-  let responsesWaitingForLoad = null;
-
-  // Return true for asynchronous functions and false for synchronous.
+  let responsesWaitingForLoad = [];
+
+  // Return true for asynchronous functions, which keeps the connection to the
+  // caller alive; Return false for synchronous functions.
   chrome.runtime.onMessageExternal.addListener(function(
       request, sender, sendResponse) {
     /**
@@ -69,49 +65,39 @@ test.util.registerRemoteTestUtils = function() {
       // handle external messages.
       return;
     }
-    if (window.IN_TEST) {
-      // If there are multiple foreground windows, the remote call API may have
-      // already been initialised by one of them, so just return true to tell
-      // the other window we are ready.
-      if ('enableTesting' in request) {
-        sendResponse(true);
-        return false;  // No need to keep the connection alive.
-      }
+
+    // Set the global IN_TEST flag, so other components are aware of it.
+    window.IN_TEST = true;
+
+    // If testing functions are loaded just run the requested function.
+    if (test.util.executeTestMessage !== null)
       return test.util.executeTestMessage(request, sendResponse);
-    }
 
-    // When a valid test extension connects, the first message sent must be an
-    // enable tests request.
-    if (!('enableTesting' in request))
-      throw new Error('Expected enableTesting');
+    // Queue the request/response pair.
+    const obj = {request, sendResponse};
+    responsesWaitingForLoad.push(obj);
 
-    if (responsesWaitingForLoad != null) {
-      // Loading started, but not complete. Queue the response.
-      responsesWaitingForLoad.push(sendResponse);
+    // Only load the script with testing functions in the first request.
+    if (responsesWaitingForLoad.length > 1)
       return true;
-    }
-    responsesWaitingForLoad = [];
 
+    // Asynchronously load the testing functions.
     let script = document.createElement('script');
     document.body.appendChild(script);
+
     script.onload = function() {
-      // The runtime load should have populated test.util with
-      // executeTestMessage, allowing it to be invoked on the next
-      // onMessageExternal call.
-      sendResponse(true);
-      responsesWaitingForLoad.forEach((queuedResponse) => {
-        queuedResponse(true);
+      // Run queued request/response pairs.
+      responsesWaitingForLoad.forEach((queueObj) => {
+        test.util.executeTestMessage(queueObj.request, queueObj.sendResponse);
       });
-      responsesWaitingForLoad = null;
-
-      // Set a global flag that we are in tests, so other components are aware
-      // of it.
-      window.IN_TEST = true;
+      responsesWaitingForLoad = [];
     };
+
     script.onerror = function(/** Event */ event) {
-      console.error('Script load failed ' + event);
-      throw new Error('Script load failed.');
+      console.error('Failed to load the run-time test script: ' + event);
+      throw new Error('Failed to load the run-time test script: ' + event);
     };
+
     const kFileManagerExtension =
         'chrome-extension://hhaomjibdihmijegdhdafkllkbggdgoj';
     const kTestScriptUrl =

ui/file_manager/integration_tests/remote_call.js

@@ -25,7 +25,6 @@ function autoStep() {
  */
 function RemoteCall(extensionId) {
   this.extensionId_ = extensionId;
-  this.testRuntimeLoaded_ = false;
 
   /**
    * Tristate holding the cached result of isStepByStepEnabled_().
@@ -52,25 +51,6 @@ RemoteCall.prototype.isStepByStepEnabled_ = function() {
   });
 };
 
-/**
- * Asks the extension under test to load its testing functions.
- * @private
- * @return {Promise<bool>}
- */
-RemoteCall.prototype.ensureLoaded_ = function() {
-  if (this.testRuntimeLoaded_)
-    return Promise.resolve(true);
-
-  return new Promise((fulfill) => {
-    chrome.runtime.sendMessage(
-        this.extensionId_, {enableTesting: true}, {}, (/** bool */ success) => {
-          chrome.test.assertTrue(success);
-          this.testRuntimeLoaded_ = success;
-          fulfill(success);
-        });
-  });
-};
-
 /**
  * Calls a remote test util in the Files app's extension. See:
  * registerRemoteTestUtils in test_util_base.js.
@@ -85,8 +65,7 @@ RemoteCall.prototype.ensureLoaded_ = function() {
  */
 RemoteCall.prototype.callRemoteTestUtil = function(
     func, appId, args, opt_callback) {
-  return this.ensureLoaded_()
-      .then(this.isStepByStepEnabled_.bind(this))
+  return this.isStepByStepEnabled_()
       .then((stepByStep) => {
         if (!stepByStep)
           return false;