Reland "Crostini Upgrader: Do not proceed if user cancels backup"

This is a reland of 9b8ade13

Original change's description:
> Crostini Upgrader: Do not proceed if user cancels backup
> 
> Previously if the user cancelled the backup, we would proceed with the
> upgrade as though the user had elected not to backup at all.
> 
> With this change, the flow will instead return to the initial screen
> when the user cancels, rather than proceed.
> 
> Bug: 1061203
> Change-Id: I7be99a2c7a6caa4b5fd143def5ba0c6f9b4d5004
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2102935
> Reviewed-by: Nicholas Verne <nverne@chromium.org>
> Commit-Queue: Nic Hollingum <hollingum@google.com>
> Cr-Commit-Position: refs/heads/master@{#750833}

Bug: 1061203
Change-Id: I983fc82b74db8cba6f2d2acf6997c8d0a2a25bc3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2109431Reviewed-by: Nicholas Verne <nverne@chromium.org>
Commit-Queue: Nic Hollingum <hollingum@google.com>
Cr-Commit-Position: refs/heads/master@{#751593}

chrome/browser/chromeos/crostini/crostini_upgrader.cc

@@ -123,11 +123,10 @@ void CrostiniUpgrader::StatusTracker::SetStatusDoneUI() {
 }
 
 void CrostiniUpgrader::StatusTracker::SetStatusCancelledUI() {
-  // Successfully canceled backup/restore. Upgrade can continue but we will not
-  // use that backup to restore from.
-  if (type() == ExportImportType::EXPORT) {
-    upgrader_->OnBackup(CrostiniResult::SUCCESS, base::nullopt);
-  } else {
+  // Cancelling the restore results in "success" i.e. we successfully didn't try
+  // to restore. Cancelling the backup is a no-op that returns you to the
+  // original screen.
+  if (type() == ExportImportType::IMPORT) {
     upgrader_->OnRestore(CrostiniResult::SUCCESS);
   }
   for (auto& observer : upgrader_->upgrader_observers_) {

chrome/browser/resources/chromeos/crostini_upgrader/app.js

@@ -106,7 +106,7 @@ Polymer({
 
     this.listenerIds_ = [
       callbackRouter.onBackupProgress.addListener((percent) => {
-        assert(this.state_ === State.BACKUP);
+        this.state_ = State.BACKUP;
         this.backupProgress_ = percent;
       }),
       callbackRouter.onBackupSucceeded.addListener((wasCancelled) => {
@@ -256,7 +256,6 @@ Polymer({
    * @private
    */
   startBackup_(showFileChooser) {
-    this.state_ = State.BACKUP;
     BrowserProxy.getInstance().handler.backup(showFileChooser);
   },
 

chrome/test/data/webui/chromeos/crostini_upgrader_app_test.js

@@ -137,7 +137,11 @@ suite('<crostini-upgrader-app>', () => {
     expectFalse(app.$$('#prompt-message').hidden);
     expectEquals(fakeBrowserProxy.handler.getCallCount('backup'), 0);
 
+    // The page will not register that backup has started until the first
+    // progress message.
     await clickAction();
+    fakeBrowserProxy.page.onBackupProgress(0);
+    await flushTasks();
     expectFalse(getProgressMessage().hidden);
     expectEquals(fakeBrowserProxy.handler.getCallCount('backup'), 1);
     expectTrue(getActionButton().hidden);
@@ -177,7 +181,11 @@ suite('<crostini-upgrader-app>', () => {
     expectFalse(app.$$('#prompt-message').hidden);
     expectEquals(fakeBrowserProxy.handler.getCallCount('backup'), 0);
 
+    // The page will not register that backup has started until the first
+    // progress message.
     await clickAction();
+    fakeBrowserProxy.page.onBackupProgress(0);
+    await flushTasks();
     expectFalse(getProgressMessage().hidden);
     expectEquals(fakeBrowserProxy.handler.getCallCount('backup'), 1);
     expectTrue(getActionButton().hidden);