Make chrome://media-app tests using loadFiles() more deterministic.

The media app has the ability to "interrupt" image decodes by revoking
Blob URLs, but this makes tests confusing.

Update the chrome://media-app tests to properly propagate the
completion of image loads on the initial loads and on navigation.

Bug: b/152729704
Change-Id: Iaca65ac183f5fd4cfa5f84be93c724266e4ae4fe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2127996Reviewed-by: dstockwell <dstockwell@chromium.org>
Commit-Queue: Trent Apted <tapted@chromium.org>
Cr-Commit-Position: refs/heads/master@{#754790}

chromeos/components/media_app_ui/resources/js/launch.js

@@ -91,14 +91,17 @@ guestMessagePipe.registerHandler(Message.DELETE_FILE, async (message) => {
   return {deleteResult: DeleteResult.SUCCESS};
 });
 
-guestMessagePipe.registerHandler(Message.NAVIGATE, (message) => {
+guestMessagePipe.registerHandler(Message.NAVIGATE, async (message) => {
   const navigate = /** @type {NavigateMessage} */ (message);
 
-  advance(navigate.direction);
+  await advance(navigate.direction);
 });
 
-/** Loads the current file list into the guest. */
-function sendFilesToGuest() {
+/**
+ * Loads the current file list into the guest.
+ * @return {!Promise<undefined>}
+ */
+async function sendFilesToGuest() {
   // Before sending to guest ensure writableFileIndex is set to be writable,
   // also clear the old token.
   if (currentlyWritableFile) {
@@ -113,7 +116,7 @@ function sendFilesToGuest() {
     // Handle can't be passed through a message pipe.
     files: currentFiles.map(fd => ({token: fd.token, file: fd.file}))
   };
-  guestMessagePipe.sendMessage(Message.LOAD_FILES, loadFilesMessage);
+  await guestMessagePipe.sendMessage(Message.LOAD_FILES, loadFilesMessage);
 }
 
 /**
@@ -185,7 +188,7 @@ async function advance(direction) {
     entryIndex += currentFiles.length;
   }
 
-  sendFilesToGuest();
+  await sendFilesToGuest();
 }
 
 document.querySelector('#prev-container')

chromeos/components/media_app_ui/resources/js/receiver.js

@@ -104,7 +104,11 @@ class ReceivedFileList {
    * @return {!Promise<undefined>}
    */
   async loadNext() {
-    parentMessagePipe.sendMessage(Message.NAVIGATE, {direction: 1});
+    // Awaiting this message send allows callers to wait for the full effects of
+    // the navigation to complete. This may include a call to load a new set of
+    // files, and the initial decode, which replaces this AbstractFileList and
+    // alters other app state.
+    await parentMessagePipe.sendMessage(Message.NAVIGATE, {direction: 1});
   }
 
   /**
@@ -112,13 +116,13 @@ class ReceivedFileList {
    * @return {!Promise<undefined>}
    */
   async loadPrev() {
-    parentMessagePipe.sendMessage(Message.NAVIGATE, {direction: -1});
+    await parentMessagePipe.sendMessage(Message.NAVIGATE, {direction: -1});
   }
 }
 
-parentMessagePipe.registerHandler(Message.LOAD_FILES, (message) => {
+parentMessagePipe.registerHandler(Message.LOAD_FILES, async (message) => {
   const filesMessage = /** @type{!LoadFilesMessage} */ (message);
-  loadFiles(new ReceivedFileList(filesMessage));
+  await loadFiles(new ReceivedFileList(filesMessage));
 });
 
 /**
@@ -147,12 +151,14 @@ function getApp() {
 /**
  * Loads a file list into the media app.
  * @param {!ReceivedFileList} fileList
+ * @return {!Promise<undefined>}
  */
 async function loadFiles(fileList) {
   const app = getApp();
   if (app) {
     await app.loadFiles(fileList);
   } else {
+    // Note we don't await in this case, which may affect b/152729704.
     window.customLaunchData = {files: fileList};
   }
 }

chromeos/components/media_app_ui/test/driver.js

@@ -196,6 +196,7 @@ function loadFile(file, handle) {
 /**
  * Helper to send multiple file to the guest.
  * @param {!Array<{file: !File, handle: !FileSystemFileHandle}>} files
+ * @return {!Promise<undefined>}
  */
 function loadMultipleFiles(files) {
   currentFiles.length = 0;
@@ -203,5 +204,5 @@ function loadMultipleFiles(files) {
     currentFiles.push({token: -1, file: f.file, handle: f.handle});
   }
   entryIndex = 0;
-  sendFilesToGuest();
+  return sendFilesToGuest();
 }

chromeos/components/media_app_ui/test/guest_query_receiver.js

@@ -141,7 +141,7 @@ function installTestHandlers() {
   const realLoadFiles = loadFiles;
   loadFiles = async (/** !ReceivedFileList */ fileList) => {
     lastReceivedFileList = fileList;
-    realLoadFiles(fileList);
+    return realLoadFiles(fileList);
   };
   signalTestHandlersReady();
 }

chromeos/components/media_app_ui/test/media_app_ui_browsertest.js

@@ -237,7 +237,7 @@ TEST_F('MediaAppUIBrowserTest', 'DeleteOriginalIPC', async () => {
 // Tests the IPC behind the loadNext and loadPrev functions on the received file
 // list in the untrusted context.
 TEST_F('MediaAppUIBrowserTest', 'NavigateIPC', async () => {
-  loadMultipleFiles([
+  await loadMultipleFiles([
     {file: await createTestImageFile(), handle: new FakeFileSystemFileHandle()},
     {file: await createTestImageFile(), handle: new FakeFileSystemFileHandle()}
   ]);