[tracing] Add a memory dump provider for DOM storage

content/browser/dom_storage/dom_storage_task_runner.h

Index: content/browser/dom_storage/dom_storage_task_runner.h
diff --git a/content/browser/dom_storage/dom_storage_task_runner.h b/content/browser/dom_storage/dom_storage_task_runner.h
index f71c9c8b63eb71a30aebf46ac7b760be09092f2a..5e21bc8aa55b86d77f94737747dddb95bc69b6d6 100644
--- a/content/browser/dom_storage/dom_storage_task_runner.h
+++ b/content/browser/dom_storage/dom_storage_task_runner.h
@@ -60,6 +60,9 @@ class CONTENT_EXPORT DOMStorageTaskRunner
     return IsRunningOnSequence(COMMIT_SEQUENCE);
   }
 
+  virtual scoped_refptr<base::SequencedTaskRunner> GetSequencedTaskRunner(
+      SequenceID sequence_id) = 0;
+
  protected:
   ~DOMStorageTaskRunner() override {}
 };
@@ -86,6 +89,9 @@ class CONTENT_EXPORT DOMStorageWorkerPoolTaskRunner :
 
   bool IsRunningOnSequence(SequenceID sequence_id) const override;
 
+  scoped_refptr<base::SequencedTaskRunner> GetSequencedTaskRunner(
+      SequenceID sequence_id) override;
+
  protected:
   ~DOMStorageWorkerPoolTaskRunner() override;
 
@@ -119,6 +125,9 @@ class CONTENT_EXPORT MockDOMStorageTaskRunner :
 
   bool IsRunningOnSequence(SequenceID sequence_id) const override;
 
+  scoped_refptr<base::SequencedTaskRunner> GetSequencedTaskRunner(
+      SequenceID sequence_id) override;
+
  protected:
   ~MockDOMStorageTaskRunner() override;