Split up and re-enable crostini settings tests

We split up the crostini tests so that each suite runs in a separate
test.

This requires factoring tests from SubPageDetails into a leaf suite
called "SubPageDefault".

We also re-enable all the tests except the Port Forwarding suite, which
we suspect is responsible for the flakes but we can not reproduce the
flakes locally.

Bug: 1056268
Change-Id: I8f4a6af5943845c67178e2fe3d9edde69fc9616f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2124281Reviewed-by: Nicholas Verne <nverne@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: Nic Hollingum <hollingum@google.com>
Cr-Commit-Position: refs/heads/master@{#754794}

chrome/test/data/webui/settings/chromeos/os_settings_browsertest.js

@@ -482,9 +482,29 @@ var OSSettingsCrostiniPageTest = class extends OSSettingsBrowserTest {
   }
 };
 
-// Disabled due to flakiness: https://crbug.com/1056268.
-TEST_F('OSSettingsCrostiniPageTest', 'DISABLED_All', () => {
-  mocha.run();
+TEST_F('OSSettingsCrostiniPageTest', 'MainPage', function() {
+  mocha.grep('MainPage').run();
+});
+
+TEST_F('OSSettingsCrostiniPageTest', 'SubPageDefault', function() {
+  mocha.grep('SubPageDefault').run();
+});
+
+TEST_F(
+    'OSSettingsCrostiniPageTest', 'DISABLED_SubPagePortForwarding', function() {
+      mocha.grep('SubPagePortForwarding').run();
+    });
+
+TEST_F('OSSettingsCrostiniPageTest', 'DiskResize', function() {
+  mocha.grep('DiskResize').run();
+});
+
+TEST_F('OSSettingsCrostiniPageTest', 'SubPageSharedPaths', function() {
+  mocha.grep('SubPageSharedPaths').run();
+});
+
+TEST_F('OSSettingsCrostiniPageTest', 'SubPageSharedUsbDevices', function() {
+  mocha.grep('SubPageSharedUsbDevices').run();
 });
 
 // Test fixture for the Date and Time page.