base: Cleanup class/struct forward declarations

base/trace_event/memory_allocator_dump.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_ALLOCATOR_DUMP_H_
 #define BASE_TRACE_EVENT_MEMORY_ALLOCATOR_DUMP_H_
 
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 
 #include "base/base_export.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/trace_event/memory_allocator_dump_guid.h"
 #include "base/values.h"
 
 namespace base {
 namespace trace_event {
 
-class MemoryDumpManager;
 class ProcessMemoryDump;
 class TracedValue;
 
 // Data model for user-land memory allocator dumps.
 class BASE_EXPORT MemoryAllocatorDump {
  public:
   enum Flags {
     DEFAULT = 0,
 
     // A dump marked weak will be discarded by TraceViewer.
@@ skipping 68 matching lines @@
   // temporary strings on each AddScalar() call.
   std::string string_conversion_buffer_;
 
   DISALLOW_COPY_AND_ASSIGN(MemoryAllocatorDump);
 };
 
 }  // namespace trace_event
 }  // namespace base
 
 #endif  // BASE_TRACE_EVENT_MEMORY_ALLOCATOR_DUMP_H_