Export all CWV* symbols from the ios/web_view dynamic library.

ios/web_view/public/cwv.h

 // Copyright 2014 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.
 
 #ifndef IOS_WEB_VIEW_PUBLIC_CWV_H_
 #define IOS_WEB_VIEW_PUBLIC_CWV_H_
 
 #import <CoreGraphics/CoreGraphics.h>
 #import <Foundation/Foundation.h>
 
+#if defined(CWV_IMPLEMENTATION)
+#include "ios/web_view/public/cwv_export.h"
+#else
+#include <ChromeWebView/cwv_export.h>
+#endif
+
 @protocol CWVDelegate;
 @class CWVWebView;
 
 // Main interface for the CWV library.
-__attribute__((visibility("default"))) @interface CWV : NSObject
+CWV_EXPORT @interface CWV : NSObject
 
 // Initializes the CWV library. This function should be called from
 // |application:didFinishLaunchingWithOptions:|.
 + (void)configureWithDelegate:(id<CWVDelegate>)delegate;
 
 // Shuts down the CWV library.  This function should be called from
 // |applicationwillTerminate:|.
 + (void)shutDown;
 
 // Creates and returns a web view.
 + (CWVWebView*)webViewWithFrame:(CGRect)frame;
 
 @end
 
 #endif  // IOS_WEB_VIEW_PUBLIC_CWV_H_