Revert to Immersive Fullscreen on OSX for a multimonitors

chrome/browser/ui/cocoa/browser_window_controller.mm

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "chrome/browser/ui/cocoa/browser_window_controller.h"
 
 #include <cmath>
 #include <numeric>
 #include <utility>
 
@@ skipping 1998 matching lines @@
   if (chrome::mac::SupportsSystemFullscreen()) {
     [self enterBrowserFullscreenWithToolbar:NO];
   } else {
     [self enterImmersiveFullscreen];
     DCHECK(!exclusiveAccessController_->url().is_empty());
     [self updateFullscreenExitBubble];
   }
 }
 
 - (void)enterWebContentFullscreen {
+  BOOL hasMultipleMonitors = [[NSScreen screens] count] > 1;

[Avi (use Gerrit), 2016/02/23 20:15:59]

Does this trigger with mirrored displays? Do we want it to?

[spqchan, 2016/02/23 21:27:59]

Good point on the mirrored displays. This should trigger when we have multiple
distinct displays.
Anyway, I just tested it with mirror displays and it seems to work fine.
However, I noticed that screen.h has a NumOfDisplays() method which gives you
the number of
distinct displays and decided to switch into that just to be safe.

+
   // HTML5 Fullscreen should only use AppKit fullscreen in 10.10+.
+  // However, if the user is using multiple monitors and turned off
+  // "Separate Space in Each Display", use Immersive Fullscreen so
+  // that the other monitors won't blank out.
   if (chrome::mac::SupportsSystemFullscreen() &&
-      base::mac::IsOSYosemiteOrLater())
+      base::mac::IsOSYosemiteOrLater() &&
+      !(hasMultipleMonitors && ![NSScreen screensHaveSeparateSpaces]))

[Avi (use Gerrit), 2016/02/23 20:15:59]

This if() needs {}s because the condition has multiple lines.

[spqchan, 2016/02/23 21:27:58]

Done.

     [self enterAppKitFullscreen];
   else
     [self enterImmersiveFullscreen];
 
   if (!exclusiveAccessController_->url().is_empty())
     [self updateFullscreenExitBubble];
 }
 
 - (void)exitAnyFullscreen {
   // TODO(erikchen): Fullscreen modes should stack. Should be able to exit
@@ skipping 93 matching lines @@
 
 - (BOOL)supportsBookmarkBar {
   return [self supportsWindowFeature:Browser::FEATURE_BOOKMARKBAR];
 }
 
 - (BOOL)isTabbedWindow {
   return browser_->is_type_tabbed();
 }
 
 @end  // @implementation BrowserWindowController(WindowType)