[memory-infra] Make MemoryDumpScheduler non-thread safe singleton

base/trace_event/memory_dump_manager.h

 // Copyright 2015 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 BASE_TRACE_EVENT_MEMORY_DUMP_MANAGER_H_
 #define BASE_TRACE_EVENT_MEMORY_DUMP_MANAGER_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 343 matching lines @@
   bool is_coordinator_;
 
   // Protects from concurrent accesses to the |dump_providers_*| and |delegate_|
   // to guard against disabling logging while dumping on another thread.
   Lock lock_;
 
   // Optimization to avoid attempting any memory dump (i.e. to not walk an empty
   // dump_providers_enabled_ list) when tracing is not enabled.
   subtle::AtomicWord memory_tracing_enabled_;
 
-  // For triggering memory dumps.
-  std::unique_ptr<MemoryDumpScheduler> dump_scheduler_;
-
   // Thread used for MemoryDumpProviders which don't specify a task runner
   // affinity.
   std::unique_ptr<Thread> dump_thread_;
 
   // The unique id of the child process. This is created only for tracing and is
   // expected to be valid only when tracing is enabled.
   uint64_t tracing_process_id_;
 
   // When true, calling |RegisterMemoryDumpProvider| is a no-op.
   bool dumper_registrations_ignored_for_testing_;
@@ skipping 25 matching lines @@
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(MemoryDumpManagerDelegate);
 };
 
 }  // namespace trace_event
 }  // namespace base
 
 #endif  // BASE_TRACE_EVENT_MEMORY_DUMP_MANAGER_H_