Reland "Don't use NOTIFICATION_BROWSER_CLOSE_CANCELLED in tests"

This relands commit 7a5df8d5

Reverting didn't fix the test, and the test was also found to have been
flaky before the original commit.

Bug: 268984, 990692
Change-Id: I26c8c264e345e0cec6e0677e9fd28517f96d0504
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1748603
Auto-Submit: Evan Stade <estade@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#687392}

chrome/browser/devtools/devtools_sanity_browsertest.cc

@@ -43,6 +43,7 @@
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_commands.h"
+#include "chrome/browser/ui/browser_list.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/common/chrome_paths.h"
 #include "chrome/common/chrome_switches.h"
@@ -786,22 +787,21 @@ IN_PROC_BROWSER_TEST_F(DevToolsBeforeUnloadTest,
       DevToolsWindowTesting::Get(windows[2])->main_web_contents());
   // Try to close second devtools.
   {
-    content::WindowedNotificationObserver cancel_browser(
-        chrome::NOTIFICATION_BROWSER_CLOSE_CANCELLED,
-        content::NotificationService::AllSources());
     chrome::CloseWindow(DevToolsWindowTesting::Get(windows[1])->browser());
     CancelModalDialog();
-    cancel_browser.Wait();
+    base::RunLoop().RunUntilIdle();
+    // The second devtools hasn't closed.
+    EXPECT_EQ(windows[1],
+              DevToolsWindow::GetInstanceForInspectedWebContents(
+                  DevToolsWindowTesting::Get(windows[0])->main_web_contents()));
   }
   // Try to close browser window.
   {
-    content::WindowedNotificationObserver cancel_browser(
-        chrome::NOTIFICATION_BROWSER_CLOSE_CANCELLED,
-        content::NotificationService::AllSources());
     chrome::CloseWindow(browser());
     AcceptModalDialog();
     CancelModalDialog();
-    cancel_browser.Wait();
+    base::RunLoop().RunUntilIdle();
+    EXPECT_EQ(browser(), BrowserList::GetInstance()->get(0));
   }
   // Try to exit application.
   {