Consolidate SDK forwards in sdk_forward_declarations.h.

content/shell/browser/shell_mac.mm

Index: content/shell/browser/shell_mac.mm
diff --git a/content/shell/browser/shell_mac.mm b/content/shell/browser/shell_mac.mm
index 5e48f26bf43845f596231a258f99eec2fafaf6c3..1c5ecb15efbcaab9f281c7c14b01ac47806fb7a3 100644
--- a/content/shell/browser/shell_mac.mm
+++ b/content/shell/browser/shell_mac.mm
@@ -8,6 +8,7 @@
 
 #include "base/logging.h"
 #import "base/mac/scoped_nsobject.h"
+#include "base/mac/sdk_forward_declarations.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/sys_string_conversions.h"
 #include "content/public/browser/native_web_keyboard_event.h"
@@ -16,16 +17,6 @@
 #import "ui/base/cocoa/underlay_opengl_hosting_window.h"
 #include "url/gurl.h"
 
-#if !defined(MAC_OS_X_VERSION_10_7) || \
-    MAC_OS_X_VERSION_MAX_ALLOWED < MAC_OS_X_VERSION_10_7
-
-enum {
-  NSWindowCollectionBehaviorFullScreenPrimary = 1 << 7,
-  NSWindowCollectionBehaviorFullScreenAuxiliary = 1 << 8
-};
-
-#endif // MAC_OS_X_VERSION_10_7
-
 // Receives notification that the window is closing so that it can start the
 // tear-down process. Is responsible for deleting itself when done.
 @interface ContentShellWindowDelegate : NSObject<NSWindowDelegate> {