Define iTunes location for media galleries tests.

chrome/browser/media_galleries/fileapi/itunes_finder_mac.h

Index: chrome/browser/media_galleries/fileapi/itunes_finder_mac.h
diff --git a/chrome/browser/media_galleries/fileapi/itunes_finder_mac.h b/chrome/browser/media_galleries/fileapi/itunes_finder_mac.h
index d123b1251dc0774576856a8d0996fbbffbec1630..b8b19e67f4c11336262e5e0ed3d13f6749fadd31 100644
--- a/chrome/browser/media_galleries/fileapi/itunes_finder_mac.h
+++ b/chrome/browser/media_galleries/fileapi/itunes_finder_mac.h
@@ -7,13 +7,19 @@
 
 #include "chrome/browser/media_galleries/fileapi/itunes_finder.h"
 
+class MacPreferences;
+
 namespace itunes {
 
+extern const char kITunesRecentDatabasePathsKey[];
+
 class ITunesFinderMac : public ITunesFinder {
  public:
   explicit ITunesFinderMac(const ITunesFinderCallback& callback);
   virtual ~ITunesFinderMac();
 
+  static void SetMacPreferencesForTesting(MacPreferences* preferences);
+
  private:
   virtual void FindITunesLibraryOnFileThread() OVERRIDE;