[Mac] Move MessagePump CrAppProtocol dependency to setup.

content/common/chrome_application_mac.mm

 // Copyright (c) 2011 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 "content/common/chrome_application_mac.h"
 
 #include "base/logging.h"
 
 @interface CrApplication ()
 - (void)setHandlingSendEvent:(BOOL)handlingSendEvent;
 @end
 
 @implementation CrApplication
 // Initialize NSApplication using the custom subclass.  Check whether NSApp
 // was already initialized using another class, because that would break
 // some things.
 + (NSApplication*)sharedApplication {
   NSApplication* app = [super sharedApplication];
-  if (![NSApp isKindOfClass:self]) {
-    DLOG(ERROR) << "NSApp should be of type " << [[self className] UTF8String]
-                << ", not " << [[NSApp className] UTF8String];
-    DCHECK(false) << "NSApp is of wrong type";
+  if (![app conformsToProtocol:@protocol(CrAppControlProtocol)]) {
+    // TODO(shess): This is necessary until all of the references to
+    // CrApplication are removed.
+    DLOG(ERROR) << "Existing NSApp (class " << [[app className] UTF8String]
+                << ") does not conform to required protocol.";
+    NOTREACHED();
   }
   return app;
 }
 
 - (BOOL)isHandlingSendEvent {
   return handlingSendEvent_;
 }
 
 - (void)setHandlingSendEvent:(BOOL)handlingSendEvent {
   handlingSendEvent_ = handlingSendEvent;
@@ skipping 10 matching lines @@
 
 @end
 
 namespace chrome_application_mac {
 
 void RegisterCrApp() {
   [CrApplication sharedApplication];
 }
 
 }  // namespace chrome_application_mac