[tracing] Allow asynchronous unregistration of unbound dump providers

base/trace_event/memory_dump_provider.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_PROVIDER_H_
 #define BASE_TRACE_EVENT_MEMORY_DUMP_PROVIDER_H_
 
 #include "base/base_export.h"
 #include "base/macros.h"
 #include "base/process/process_handle.h"
@@ skipping 18 matching lines @@
     Options() : target_pid(kNullProcessId) {}
     explicit Options(ProcessId target_pid) : target_pid(target_pid) {}
 
     // If the dump provider generates dumps on behalf of another process,
     // |target_process| contains the pid of that process.
     // The default value is kNullProcessId, which means that the dump provider
     // generates dumps for the current process.
     ProcessId target_pid;
   };
 
+  virtual ~MemoryDumpProvider() {}
+
   // Called by the MemoryDumpManager when generating memory dumps.
   // The |args| specify if the embedder should generate light/heavy dumps on
   // dump requests. The embedder should return true if the |pmd| was
   // successfully populated, false if something went wrong and the dump should
   // be considered invalid.
   // (Note, the MemoryDumpManager has a fail-safe logic which will disable the
   // MemoryDumpProvider for the entire trace session if it fails consistently).
   virtual bool OnMemoryDump(const MemoryDumpArgs& args,
                             ProcessMemoryDump* pmd) = 0;
 
   // Called by the MemoryDumpManager when an allocator should start or stop
   // collecting extensive allocation data, if supported.
   virtual void OnHeapProfilingEnabled(bool enabled) {}
 
  protected:
   MemoryDumpProvider() {}
-  virtual ~MemoryDumpProvider() {}
 
   DISALLOW_COPY_AND_ASSIGN(MemoryDumpProvider);
 };
 
 }  // namespace trace_event
 }  // namespace base
 
 #endif  // BASE_TRACE_EVENT_MEMORY_DUMP_PROVIDER_H_