Revert to Immersive Fullscreen on OSX for a special case

chrome/browser/ui/cocoa/browser_window_controller.mm

Index: chrome/browser/ui/cocoa/browser_window_controller.mm
diff --git a/chrome/browser/ui/cocoa/browser_window_controller.mm b/chrome/browser/ui/cocoa/browser_window_controller.mm
index 9c2e44caec95387216fae9443df51c1b6bf20216..5821448fb1777c725dc60c067531448a36030d0e 100644
--- a/chrome/browser/ui/cocoa/browser_window_controller.mm
+++ b/chrome/browser/ui/cocoa/browser_window_controller.mm
@@ -100,6 +100,7 @@
 #include "ui/base/l10n/l10n_util_mac.h"
 #import "ui/gfx/mac/coordinate_conversion.h"
 #include "ui/gfx/mac/scoped_cocoa_disable_screen_updates.h"
+#include "ui/gfx/screen.h"
 
 using bookmarks::BookmarkModel;
 using bookmarks::BookmarkNode;
@@ -2026,11 +2027,18 @@ willAnimateFromState:(BookmarkBar::State)oldState
 - (void)enterWebContentFullscreenForURL:(const GURL&)url
                              bubbleType:(ExclusiveAccessBubbleType)bubbleType {
   // 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.
+  gfx::Screen* screen = gfx::Screen::GetScreen();
+  BOOL hasMultipleMonitors = screen && screen->GetNumDisplays() > 1;
   if (chrome::mac::SupportsSystemFullscreen() &&
-      base::mac::IsOSYosemiteOrLater())
+      base::mac::IsOSYosemiteOrLater() &&
+      !(hasMultipleMonitors && ![NSScreen screensHaveSeparateSpaces])) {
     [self enterAppKitFullscreen];
-  else
+  } else {
     [self enterImmersiveFullscreen];
+  }
 
   if (!url.is_empty())
     [self updateFullscreenExitBubbleURL:url bubbleType:bubbleType];