[tracing] Add a memory dump provider for DOM storage

content/browser/dom_storage/dom_storage_namespace.h

Index: content/browser/dom_storage/dom_storage_namespace.h
diff --git a/content/browser/dom_storage/dom_storage_namespace.h b/content/browser/dom_storage/dom_storage_namespace.h
index 238b7ca554e75c65c94d646cf6963b71457049af..68fcd43b7c643ce3f6ca3b52dd5ae85533745f42 100644
--- a/content/browser/dom_storage/dom_storage_namespace.h
+++ b/content/browser/dom_storage/dom_storage_namespace.h
@@ -12,6 +12,7 @@
 
 #include "base/files/file_path.h"
 #include "base/memory/ref_counted.h"
+#include "base/trace_event/memory_dump_provider.h"
 #include "content/common/content_export.h"
 #include "url/gurl.h"
 
@@ -24,7 +25,8 @@ class SessionStorageDatabase;
 // Container for the set of per-origin Areas.
 // See class comments for DOMStorageContextImpl for a larger overview.
 class CONTENT_EXPORT DOMStorageNamespace
-    : public base::RefCountedThreadSafe<DOMStorageNamespace> {
+    : public base::RefCountedThreadSafe<DOMStorageNamespace>,
+      public base::trace_event::MemoryDumpProvider {
  public:
   // Option for PurgeMemory.
   enum PurgeOption {
@@ -76,6 +78,10 @@ class CONTENT_EXPORT DOMStorageNamespace
 
   unsigned int CountInMemoryAreas() const;
 
+  // base::trace_event::MemoryDumpProvider implementation.
+  bool OnMemoryDump(const base::trace_event::MemoryDumpArgs& args,
+                    base::trace_event::ProcessMemoryDump* pmd) override;
+
  private:
   friend class base::RefCountedThreadSafe<DOMStorageNamespace>;
 
@@ -91,7 +97,7 @@ class CONTENT_EXPORT DOMStorageNamespace
   };
   typedef std::map<GURL, AreaHolder> AreaMap;
 
-  ~DOMStorageNamespace();
+  ~DOMStorageNamespace() override;
 
   // Returns a pointer to the area holder in our map or NULL.
   AreaHolder* GetAreaHolder(const GURL& origin);