chromeos: Destruct DriveResourceMetadata on the blocking pool

chrome/browser/chromeos/drive/drive_resource_metadata.h

Index: chrome/browser/chromeos/drive/drive_resource_metadata.h
diff --git a/chrome/browser/chromeos/drive/drive_resource_metadata.h b/chrome/browser/chromeos/drive/drive_resource_metadata.h
index 33729979d8d07821231940887bc33f7ca03a7f4e..af213b4ac502dc2f3b6f8a0da4dc1703e3891196 100644
--- a/chrome/browser/chromeos/drive/drive_resource_metadata.h
+++ b/chrome/browser/chromeos/drive/drive_resource_metadata.h
@@ -137,7 +137,10 @@ class DriveResourceMetadata {
   DriveResourceMetadata(
       const std::string& root_resource_id,
       scoped_refptr<base::SequencedTaskRunner> blocking_task_runner);
-  virtual ~DriveResourceMetadata();
+
+  // Destroys this object.  This method posts a task to |blocking_task_runner_|
+  // to safely delete this object.
+  void Destroy();
 
   // True if the file system feed is loaded from the cache or from the server.
   bool loaded() const { return loaded_; }
@@ -234,6 +237,12 @@ class DriveResourceMetadata {
  private:
   friend class DriveResourceMetadataTest;
 
+  // Note: Use Destroy() to delete this object.
+  virtual ~DriveResourceMetadata();
+
+  // Used to implement Destroy().
+  void DestroyOnBlockingPool();
+
   // Clears root_ and the resource map.
   void ClearRoot();