Separate ProxyResolverMac and ProxyConfigServiceMac into their own files

base/mac_util.h

Index: base/mac_util.h
===================================================================
--- base/mac_util.h	(revision 34241)
+++ base/mac_util.h	(working copy)
@@ -92,6 +92,12 @@
 // Set the Time Machine exclusion property for the given file.
 bool SetFileBackupExclusion(const FilePath& file_path, bool exclude);
 
+// Utility function to pull out a value from a dictionary, check its type, and
+// return it.  Returns NULL if the key is not present or of the wrong type.
+CFTypeRef GetValueFromDictionary(CFDictionaryRef dict,
+                                 CFStringRef key,
+                                 CFTypeID expected_type);
+
 }  // namespace mac_util
 
 #endif  // BASE_MAC_UTIL_H_