Revert "Mac: exit browser fullscreen on Esc"

This reverts commit a9f47ca.

Reason for revert: https://crbug.com/1077651

Original change's description:
> Mac: exit browser fullscreen on Esc
> 
> Every (non-Chrome) Mac app I've tried supports this, and nobody seems to
> know of a good reason for why we don't do it, so let's do it.
> 
> Bug: 1074609
> Change-Id: I43e9b5137faf347e17e737e2e3f2cbdba4e6c470
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2174345
> Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
> Commit-Queue: Leonard Grey <lgrey@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#764644}

TBR=ellyjones@chromium.org,lgrey@chromium.org

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

Bug: 1074609
Change-Id: I9825e3f24975563333e35263b22316b3c25a6a88
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2179663
Reviewed-by: Leonard Grey <lgrey@chromium.org>
Commit-Queue: Leonard Grey <lgrey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#765065}

chrome/browser/ui/exclusive_access/fullscreen_controller.cc

@@ -274,14 +274,10 @@ bool FullscreenController::HandleUserPressedEscape() {
     return true;
   }
 
-// On macOS, it's idiomatic to exit application fullscreen on Esc.
-#if !defined(OS_MACOSX)
   if (!IsWindowFullscreenForTabOrPending())
     return false;
-  ExitFullscreenModeForTab(exclusive_access_tab());
-#else
-  ExitExclusiveAccessToPreviousState();
-#endif
+
+  ExitExclusiveAccessIfNecessary();
   return true;
 }