[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..577fd6872e37c35176c9fe3e56fafb83f401af07 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 {
@@ -23,8 +27,20 @@ class BASE_EXPORT DiscardableMemoryAllocator {
   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