Make MediaFileUtil run on thread pool.

webkit/fileapi/isolated_mount_point_provider.h

Index: webkit/fileapi/isolated_mount_point_provider.h
diff --git a/webkit/fileapi/isolated_mount_point_provider.h b/webkit/fileapi/isolated_mount_point_provider.h
index 0bd5182afd45624cd112327a4281730e2a3298ff..e3546f7e4a2d1d02acf2f0b8c50a0eead63ef726 100644
--- a/webkit/fileapi/isolated_mount_point_provider.h
+++ b/webkit/fileapi/isolated_mount_point_provider.h
@@ -8,8 +8,13 @@
 #include <vector>
 
 #include "base/memory/scoped_ptr.h"
+#include "base/memory/ref_counted.h"
 #include "webkit/fileapi/file_system_mount_point_provider.h"
 
+namespace base {
+class SequencedTaskRunner;
+}
+
 namespace fileapi {
 
 class DraggedFileUtil;
@@ -23,7 +28,8 @@ class IsolatedMountPointProvider : public FileSystemMountPointProvider {
   typedef FileSystemMountPointProvider::ValidateFileSystemCallback
       ValidateFileSystemCallback;
 
-  IsolatedMountPointProvider();
+  explicit IsolatedMountPointProvider(
+      base::SequencedTaskRunner* media_task_runner);
   virtual ~IsolatedMountPointProvider();
 
   // FileSystemMountPointProvider implementation.
@@ -60,6 +66,8 @@ class IsolatedMountPointProvider : public FileSystemMountPointProvider {
  private:
   scoped_ptr<MediaPathFilter> media_path_filter_;
 
+  scoped_refptr<base::SequencedTaskRunner> media_task_runner_;
+
   scoped_ptr<IsolatedFileUtil> isolated_file_util_;
   scoped_ptr<DraggedFileUtil> dragged_file_util_;
   scoped_ptr<NativeMediaFileUtil> native_media_file_util_;