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

base/memory/discardable_memory_allocator.h

Index: base/memory/discardable_memory_allocator.h
diff --git a/base/memory/discardable_memory_allocator.h b/base/memory/discardable_memory_allocator.h
index 400f87aeee0d49f7b1699ac0d4ed420f2388ca45..7e08b7138675fde55e6ace5c739aa00248e5a98f 100644
--- a/base/memory/discardable_memory_allocator.h
+++ b/base/memory/discardable_memory_allocator.h
@@ -9,6 +9,10 @@
 #include "base/memory/scoped_ptr.h"
 
 namespace base {
+namespace trace_event {
+class ProcessMemoryDump;
+}
+
 class DiscardableMemory;
 
 class BASE_EXPORT DiscardableMemoryAllocator {
@@ -23,6 +27,10 @@ class BASE_EXPORT DiscardableMemoryAllocator {
   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() {}
 };