(2nd try) Add a helper class that keeps per-profile information for FileSystem API

chrome/test/testing_profile.h

Index: chrome/test/testing_profile.h
diff --git a/chrome/test/testing_profile.h b/chrome/test/testing_profile.h
index a080bd590391aba37b4e5cf3f211c9de41ddd4a4..6399692db7bd2844f9843993ab13708da3e84282 100644
--- a/chrome/test/testing_profile.h
+++ b/chrome/test/testing_profile.h
@@ -156,6 +156,7 @@ class TestingProfile : public Profile {
   virtual history::TopSites* GetTopSites();
   virtual DownloadManager* GetDownloadManager() { return NULL; }
   virtual PersonalDataManager* GetPersonalDataManager() { return NULL; }
+  virtual FileSystemHostContext* GetFileSystemHostContext() { return NULL; }
   virtual bool HasCreatedDownloadManager() const { return false; }
   virtual void InitThemes();
   virtual void SetTheme(Extension* extension) {}