[Mac] Avoid "adding unknown subview" warning.

chrome/browser/ui/cocoa/full_size_content_window.mm

Index: chrome/browser/ui/cocoa/full_size_content_window.mm
diff --git a/chrome/browser/ui/cocoa/full_size_content_window.mm b/chrome/browser/ui/cocoa/full_size_content_window.mm
index eddf7f4da1d0e43fc21445e9e28ce0015f547f29..42753be1b62a195397150edc15f2801bab3d18e2 100644
--- a/chrome/browser/ui/cocoa/full_size_content_window.mm
+++ b/chrome/browser/ui/cocoa/full_size_content_window.mm
@@ -9,6 +9,7 @@
 #include "base/auto_reset.h"
 #include "base/logging.h"
 #include "base/mac/foundation_util.h"
+#include "base/mac/mac_util.h"
 #include "base/mac/scoped_objc_class_swizzler.h"
 
 @interface FullSizeContentWindow ()
@@ -139,20 +140,22 @@ static IMP g_original_callstacksymbols_implementation;
       [self setContentView:chromeWindowView_];
       [chromeWindowView_ setFrame:[[chromeWindowView_ superview] bounds]];
 
-      // Our content view overlaps the window control buttons, so we must ensure
-      // it is positioned below the buttons.
-      NSView* superview = [chromeWindowView_ superview];
-      [chromeWindowView_ removeFromSuperview];
+      if (base::mac::IsAtMostOS10_10()) {
+        // Our content view overlaps the window control buttons, so we must
+        // ensure it is positioned below the buttons.
+        NSView* superview = [chromeWindowView_ superview];
+        [chromeWindowView_ removeFromSuperview];
 
-      // Prevent the AppKit from generating a backtrace to include in it's
-      // complaint about our upcoming call to addSubview:positioned:relativeTo:.
-      // See +load for more info.
-      base::AutoReset<bool> disable_symbolication(&g_disable_callstacksymbols,
-                                                  true);
+        // Prevent the AppKit from generating a backtrace to include in it's
+        // complaint about our upcoming call to
+        // addSubview:positioned:relativeTo:. See +load for more info.
+        base::AutoReset<bool> disable_symbolication(&g_disable_callstacksymbols,
+                                                    true);
 
-      [superview addSubview:chromeWindowView_
-                 positioned:NSWindowBelow
+        [superview addSubview:chromeWindowView_
+                   positioned:NSWindowBelow
                  relativeTo:nil];
+      }
     }
   }
   return self;