[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;
 
+  // Used by other allocators to expess sub-allocation from discardable memory

[reveman, 2015/07/30 21:27:56]

express

[ssid, 2015/07/31 12:59:40]

Done.

+  // heap for tracing. To expess any suballocation, the dump providers need to
+  // create a sub-allocation edge from this node.
+  // E.g.: ProcessMemoryDump::AddSuballocation(skia_dump_guid,
+  //                                           GetMemoryPoolNameForTracing());

[reveman, 2015/07/30 21:27:56]

Not sure we need this much detail in this comment. A reference to "skia" in
base/ feels a bit awkward. How about simply:

// Returns the memory pool name used by discardable memory allocators for
tracing purposes.


and the details for how to use that can be documented somewhere else.

[ssid, 2015/07/31 12:59:40]

Done.

+  static const char* GetMemoryPoolNameForTracing();
+
  protected:
   virtual ~DiscardableMemoryAllocator() {}
+
+  // Used by the discqardable allocator implementation to create the memory dump
+  // of the memory pool, for tracing.
+  static void CreateMemoryPoolDumpForTracing(
+      trace_event::ProcessMemoryDump* pmd);

[reveman, 2015/07/30 21:27:56]

Not sure it's worth having this here just for code reuse. See my other comment.

[ssid, 2015/07/31 12:59:40]

Moved it to the impl. Thanks

 };
 
 }  // namespace base
 
 #endif  // BASE_MEMORY_DISCARDABLE_MEMORY_ALLOCATOR_H_