[tracing] Add memory statistics from level db clients to tracing.

extensions/browser/value_store/leveldb_value_store.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef EXTENSIONS_BROWSER_VALUE_STORE_LEVELDB_VALUE_STORE_H_
 #define EXTENSIONS_BROWSER_VALUE_STORE_LEVELDB_VALUE_STORE_H_
 
 #include <string>
 #include <vector>
 
 #include "base/compiler_specific.h"
 #include "base/files/file_path.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/trace_event/memory_dump_provider.h"
 #include "extensions/browser/value_store/value_store.h"
 #include "third_party/leveldatabase/src/include/leveldb/db.h"
 
 namespace base {
 class HistogramBase;
 }  // namespace base
 
 // Value store area, backed by a leveldb database.
 // All methods must be run on the FILE thread.
-class LeveldbValueStore : public ValueStore {
+class LeveldbValueStore : public ValueStore,
+                          public base::trace_event::MemoryDumpProvider {
  public:
   // Creates a database bound to |path|. The underlying database won't be
   // opened (i.e. may not be created) until one of the get/set/etc methods are
   // called - this is because opening the database may fail, and extensions
   // need to be notified of that, but we don't want to permanently give up.
   //
   // Must be created on the FILE thread.
   LeveldbValueStore(const std::string& uma_client_name,
                     const base::FilePath& path);
 
@@ skipping 15 matching lines @@
   WriteResult Remove(const std::string& key) override;
   WriteResult Remove(const std::vector<std::string>& keys) override;
   WriteResult Clear() override;
   bool Restore() override;
   bool RestoreKey(const std::string& key) override;
 
   // Write directly to the backing levelDB. Only used for testing to cause
   // corruption in the database.
   bool WriteToDbForTest(leveldb::WriteBatch* batch);
 
+  // base::trace_event::MemoryDumpProvider implementation.
+  bool OnMemoryDump(const base::trace_event::MemoryDumpArgs& args,
+                    base::trace_event::ProcessMemoryDump* pmd) override;
+
  private:
   // Tries to open the database if it hasn't been opened already.
   scoped_ptr<ValueStore::Error> EnsureDbIsOpen();
 
   // Reads a setting from the database.
   scoped_ptr<ValueStore::Error> ReadFromDb(
       leveldb::ReadOptions options,
       const std::string& key,
       // Will be reset() with the result, if any.
       scoped_ptr<base::Value>* setting);
@@ skipping 26 matching lines @@
   const base::FilePath db_path_;
 
   // leveldb backend.
   scoped_ptr<leveldb::DB> db_;
   base::HistogramBase* open_histogram_;
 
   DISALLOW_COPY_AND_ASSIGN(LeveldbValueStore);
 };
 
 #endif  // EXTENSIONS_BROWSER_VALUE_STORE_LEVELDB_VALUE_STORE_H_