Fix PathServiceTest.Get on iOS.

base/base_paths_mac.mm

 // Copyright (c) 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.
 
 // Defines base::PathProviderMac which replaces base::PathProviderPosix for Mac
 // in base/path_service.cc.
 
 #include <dlfcn.h>
 #import <Foundation/Foundation.h>
 #include <mach-o/dyld.h>
@@ skipping 74 matching lines @@
         // src/xcodebuild/{Debug|Release}/Chromium.app/Contents/MacOS/Chromium
         *result = result->DirName().DirName().DirName().DirName().DirName();
       } else {
         // Unit tests execute two levels deep from the source root, eg:
         // src/xcodebuild/{Debug|Release}/base_unittests
         *result = result->DirName().DirName();
       }
 #endif
       return true;
     case base::DIR_USER_DESKTOP:
+#if defined(OS_IOS)
+      // iOS does not have desktop directories.
+      NOTIMPLEMENTED();
+      return false;
+#else
       return base::mac::GetUserDirectory(NSDesktopDirectory, result);
+#endif
     case base::DIR_CACHE:
       return base::mac::GetUserDirectory(NSCachesDirectory, result);
     case base::DIR_HOME:
       *result = base::mac::NSStringToFilePath(NSHomeDirectory());
       return true;
     default:
       return false;
   }
 }
 
 }  // namespace base