Revert "Don't use NOTIFICATION_BROWSER_CLOSE_CANCELLED in tests"

This reverts commit 7a5df8d5.

Reason for revert: Suspect it introduces timeout https://crbug.com/990692

DevToolsSanityTest.TestDeviceEmulation is reliably timing out with
"[FAILED] Timeout exceeded: 20 sec".

Original change's description:
> Don't use NOTIFICATION_BROWSER_CLOSE_CANCELLED in tests
> 
> Bug: 268984
> Change-Id: Ie41cb913d29ad690b9364d9c478c7a3c4771f607
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1730591
> Reviewed-by: Avi Drissman <avi@chromium.org>
> Commit-Queue: Evan Stade <estade@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#683662}

TBR=avi@chromium.org,estade@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 268984, 990692
Change-Id: Ia1213f589b2cf3b966381886f2d60ff646ae7103
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1734735Reviewed-by: Matt Giuca <mgiuca@chromium.org>
Commit-Queue: Matt Giuca <mgiuca@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683935}

chrome/browser/devtools/devtools_sanity_browsertest.cc

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