[Mac] Add cocoa implementation for sidebar extension action support

chrome/browser/ui/cocoa/browser_window_controller_unittest.mm

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "chrome/browser/ui/cocoa/browser_window_controller.h"
 
 #include "base/mac/mac_util.h"
 #import "base/mac/scoped_nsobject.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/pref_service.h"
@@ skipping 42 matching lines @@
 }
 
 - (NSView*)bookmarkView {
   return [bookmarkBarController_ view];
 }
 
 - (NSView*)findBarView {
   return [findBarCocoaController_ view];
 }
 
+- (NSView*)sidebarView {
+  return [sidebarController_ view];
+}
+
 - (BOOL)bookmarkBarVisible {
   return [bookmarkBarController_ isVisible];
 }
 @end
 
 class BrowserWindowControllerTest : public CocoaProfileTest {
  public:
   void SetUp() override {
     CocoaProfileTest::SetUp();
     ASSERT_TRUE(browser());
@@ skipping 748 matching lines @@
       [[NSWindow alloc] initWithContentRect:NSMakeRect(0,0,400,400)
                                   styleMask:NSBorderlessWindowMask
                                     backing:NSBackingStoreBuffered
                                       defer:NO]);
   [[testFullscreenWindow_ contentView] setWantsLayer:YES];
   return testFullscreenWindow_.get();
 }
 @end
 
 /* TODO(???): test other methods of BrowserWindowController */