[iOS] Get unit tests passing with multiwindow enabled.

In order for the unit test suites to run with the iOS 13 Scene APIs:

- Create a test-specific scene delegate (similar to the test-specific
  app delegate). For now, this is a no-op delegate.

- Update the plist for unittests using the scene APIs to use this as
  the scene delegate.

- Early return from one test that uses a code path that expects
  SceneState objects to be created.

Bug: 1084483
Change-Id: Ibd0efbc72b55818647076481b361b3252e847520
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2241652Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#783002}

base/test/test_support_ios.mm

@@ -50,6 +50,16 @@ static char** g_argv;
 @end
 #endif  // TARGET_IPHONE_SIMULATOR
 
+// No-op scene delegate for unit tests. Note that this is created along with
+// the application delegate, so they need to be separate objects (the same
+// object can't be both the app and scene delegate, since new scene delegates
+// are created for each scene).
+@interface ChromeUnitTestSceneDelegate : NSObject <UISceneDelegate>
+@end
+
+@implementation ChromeUnitTestSceneDelegate
+@end
+
 @interface ChromeUnitTestDelegate : NSObject <GoogleTestRunnerDelegate> {
   base::scoped_nsobject<UIWindow> _window;
 }

ios/chrome/app/BUILD.gn

@@ -53,6 +53,7 @@ source_set("unit_tests") {
     "//ios/chrome/browser/browser_state:test_support",
     "//ios/chrome/browser/tabs",
     "//ios/chrome/browser/ui/main:scene",
+    "//ios/chrome/browser/ui/util:multiwindow_util",
     "//ios/chrome/common/app_group",
     "//ios/chrome/test:test_support",
     "//ios/public/provider/chrome/browser:browser",

ios/chrome/app/main_application_delegate_unittest.mm

@@ -8,6 +8,7 @@
 
 #import "base/mac/foundation_util.h"
 #import "ios/chrome/app/chrome_overlay_window_testing.h"
+#import "ios/chrome/browser/ui/util/multi_window_support.h"
 #include "ios/public/provider/chrome/browser/chrome_browser_provider.h"
 #include "testing/platform_test.h"
 #import "third_party/ocmock/OCMock/OCMock.h"
@@ -22,6 +23,11 @@ using MainApplicationDelegateTest = PlatformTest;
 // is called when the application is launched in background.
 // http://crbug.com/437307
 TEST_F(MainApplicationDelegateTest, CrashIfNotInitialized) {
+  // Skip for scene API for now.
+  // TODO(crbug.com/1093755) : Support this test in with the scene API.
+  if (IsSceneStartupSupported())
+    return;
+
   // Save both ChromeBrowserProvider as MainController register new instance.
   ios::ChromeBrowserProvider* stashed_chrome_browser_provider =
       ios::GetChromeBrowserProvider();

ios/chrome/test/unittest-scene-lifecycle-Info.plist

@@ -185,7 +185,7 @@
                                   <key>UISceneClassName</key>
                                   <string>UIWindowScene</string>
                                   <key>UISceneDelegateClassName</key>
-                                        <string>SceneDelegate</string>
+                                  <string>ChromeUnitTestSceneDelegate</string>
                                   <key>UISceneConfigurationName</key>
                                   <string>Default Configuration</string>
                                   <key>UILaunchStoryboardName</key>