[tracing] Add SkResourceCache as suballocation to avoid double counting.

base/memory/discardable_memory_allocator.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_MEMORY_DISCARDABLE_MEMORY_ALLOCATOR_H_
 #define BASE_MEMORY_DISCARDABLE_MEMORY_ALLOCATOR_H_
 
 #include "base/base_export.h"
 #include "base/memory/scoped_ptr.h"
 
 namespace base {
+namespace trace_event {
+class ProcessMemoryDump;
+}
+
 class DiscardableMemory;
 
 class BASE_EXPORT DiscardableMemoryAllocator {
  public:
   // Returns the allocator instance.
   static DiscardableMemoryAllocator* GetInstance();
 
   // Sets the allocator instance. Can only be called once, e.g. on startup.
   // Ownership of |instance| remains with the caller.
   static void SetInstance(DiscardableMemoryAllocator* allocator);
 
   virtual scoped_ptr<DiscardableMemory> AllocateLockedDiscardableMemory(
       size_t size) = 0;
 
+  // Returns the memory pool name used by discardable memory allocators for
+  // tracing purposes.
+  static const char* GetMemoryPoolNameForTracing();
+
  protected:
   virtual ~DiscardableMemoryAllocator() {}
 };
 
 }  // namespace base
 
 #endif  // BASE_MEMORY_DISCARDABLE_MEMORY_ALLOCATOR_H_