Remove all the OS X 10.6 SDK forward declarations.

chrome/browser/ui/panels/panel_window_controller_cocoa.mm

Index: chrome/browser/ui/panels/panel_window_controller_cocoa.mm
diff --git a/chrome/browser/ui/panels/panel_window_controller_cocoa.mm b/chrome/browser/ui/panels/panel_window_controller_cocoa.mm
index 72c8825a5aee6f9386d7d218aae700ab9de93791..c86cf9f661aa2c6314d719fd7a468aac4856614f 100644
--- a/chrome/browser/ui/panels/panel_window_controller_cocoa.mm
+++ b/chrome/browser/ui/panels/panel_window_controller_cocoa.mm
@@ -54,16 +54,6 @@ const double kWidthOfMouseResizeArea = 4.0;
 // down before panel resizing operation actually starts.
 const double kDragThreshold = 3.0;
 
-// Replicate specific 10.6 SDK declarations for building with prior SDKs.
-#if !defined(MAC_OS_X_VERSION_10_6) || \
-    MAC_OS_X_VERSION_MAX_ALLOWED < MAC_OS_X_VERSION_10_6
-
-enum {
-  NSWindowCollectionBehaviorParticipatesInCycle = 1 << 5
-};
-
-#endif  // MAC_OS_X_VERSION_10_6
-
 @interface PanelWindowControllerCocoa (PanelsCanBecomeKey)
 // Internal helper method for extracting the total number of panel windows
 // from the panel manager. Used to decide if panel can become the key window.