[Mac] Add cocoa implementation for sidebar extension action support

chrome/browser/ui/cocoa/browser_window_controller.h

Index: chrome/browser/ui/cocoa/browser_window_controller.h
diff --git a/chrome/browser/ui/cocoa/browser_window_controller.h b/chrome/browser/ui/cocoa/browser_window_controller.h
index 514f4ee9518b9849836461fab46d74b965ea456a..1e76124b8deeacb92d19f07334c1812e6f86eafc 100644
--- a/chrome/browser/ui/cocoa/browser_window_controller.h
+++ b/chrome/browser/ui/cocoa/browser_window_controller.h
@@ -44,6 +44,7 @@ class LocationBarViewMac;
 @class OverlayableContentsController;
 class PermissionBubbleCocoa;
 @class PresentationModeController;
+@class SidebarController;
 class StatusBubbleMac;
 @class TabStripController;
 @class TabStripView;
@@ -85,6 +86,8 @@ class Command;
   base::scoped_nsobject<BrowserWindowFullscreenTransition>
       fullscreenTransition_;
 
+  base::scoped_nsobject<SidebarController> sidebarController_;
+
   // Strong. StatusBubble is a special case of a strong reference that
   // we don't wrap in a scoped_ptr because it is acting the same
   // as an NSWindowController in that it wraps a window that must
@@ -341,6 +344,11 @@ class Command;
 // Shows or hides the docked web inspector depending on |contents|'s state.
 - (void)updateDevToolsForContents:(content::WebContents*)contents;
 
+// Displays the active sidebar linked to the |tab_contents| with
+// |sidebar_contents| or hides sidebar UI if there's no sidebar contents.
+- (void)updateSidebarForContents:(content::WebContents*)tab_contents
+                sidebar_contents:(content::WebContents*)sidebar_contents;
+
 // Gets the current theme provider.
 - (ui::ThemeProvider*)themeProvider;