[FileAPI] Replace default leveldb::Env with leveldb::MemEnv in tests.

chrome/browser/sync_file_system/local/canned_syncable_file_system.h

Index: chrome/browser/sync_file_system/local/canned_syncable_file_system.h
diff --git a/chrome/browser/sync_file_system/local/canned_syncable_file_system.h b/chrome/browser/sync_file_system/local/canned_syncable_file_system.h
index 0ef388d711d6808870930b89639586c9b5a03b3d..a32dd34582c4874eba5a511eaf37e8d89a097ff3 100644
--- a/chrome/browser/sync_file_system/local/canned_syncable_file_system.h
+++ b/chrome/browser/sync_file_system/local/canned_syncable_file_system.h
@@ -35,6 +35,10 @@ class FileSystemOperationRunner;
 class FileSystemURL;
 }
 
+namespace leveldb {
+class Env;
+}
+
 namespace net {
 class URLRequestContext;
 }
@@ -64,6 +68,7 @@ class CannedSyncableFileSystem
   typedef fileapi::FileSystemOperation::FileEntryList FileEntryList;
 
   CannedSyncableFileSystem(const GURL& origin,
+                           leveldb::Env* env_override,
                            base::SingleThreadTaskRunner* io_task_runner,
                            base::SingleThreadTaskRunner* file_task_runner);
   virtual ~CannedSyncableFileSystem();
@@ -225,6 +230,7 @@ class CannedSyncableFileSystem
   base::File::Error result_;
   sync_file_system::SyncStatusCode sync_status_;
 
+  leveldb::Env* env_override_;
   scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
   scoped_refptr<base::SingleThreadTaskRunner> file_task_runner_;