[tracing] Introduce support for userland memory allocators dumps.

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/trace_event/memory_allocator_attributes.h"
 
 namespace base {
 namespace trace_event {
 
 class ProcessMemoryDump;
 
 // The contract interface that memory dump providers must implement.
 class BASE_EXPORT MemoryDumpProvider {
  public:
   // Called by the MemoryDumpManager when generating dump points.
   // Returns: true if the |pmd| was successfully populated, false otherwise.
   virtual bool DumpInto(ProcessMemoryDump* pmd) = 0;
 
   virtual const char* GetFriendlyName() const = 0;
 
+  const MemoryAllocatorDeclaredAttributes& allocator_attributes() const {
+    return allocator_attributes_;
+  }
+
  protected:
-  MemoryDumpProvider() {}
-  virtual ~MemoryDumpProvider() {}
+  MemoryDumpProvider();
+  virtual ~MemoryDumpProvider();
+
+  void DeclareAllocatorAttribute(const MemoryAllocatorDeclaredAttribute& attr);
 
  private:
+  // The map (attribute name -> type) that specifies the semantic of the
+  // extra attributes that the MemoryAllocatorDump(s) produced by this
+  // MemoryDumpProvider will have.
+  MemoryAllocatorDeclaredAttributes allocator_attributes_;
+
   DISALLOW_COPY_AND_ASSIGN(MemoryDumpProvider);
 };
 
 }  // namespace trace_event
 }  // namespace base
 
 #endif  // BASE_TRACE_EVENT_MEMORY_DUMP_PROVIDER_H_