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

base/memory/discardable_memory_allocator.cc

Index: base/memory/discardable_memory_allocator.cc
diff --git a/base/memory/discardable_memory_allocator.cc b/base/memory/discardable_memory_allocator.cc
index 002a3ba5e4763c360dc0a96861d0c53758bdb3bc..99363fe40dfcaa9fbc6124258f2526b9b6be85a3 100644
--- a/base/memory/discardable_memory_allocator.cc
+++ b/base/memory/discardable_memory_allocator.cc
@@ -5,6 +5,8 @@
 #include "base/memory/discardable_memory_allocator.h"
 
 #include "base/logging.h"
+#include "base/trace_event/memory_allocator_dump.h"
+#include "base/trace_event/process_memory_dump.h"
 
 namespace base {
 namespace {
@@ -31,4 +33,24 @@ DiscardableMemoryAllocator* DiscardableMemoryAllocator::GetInstance() {
   return g_allocator;
 }
 
+// static
+const char* DiscardableMemoryAllocator::GetMemoryPoolNameForTracing() {
+  return "discardable/allocated_objects";
+}
+
+// static
+void DiscardableMemoryAllocator::CreateMemoryPoolDumpForTracing(
+    trace_event::ProcessMemoryDump* pmd) {
+  base::trace_event::MemoryAllocatorDump* objects_dump =
+      pmd->CreateAllocatorDump(GetMemoryPoolNameForTracing());
+  base::trace_event::MemoryAllocatorDump* discardable_segments_dump =
+      pmd->CreateAllocatorDump("discardable/segments");

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

The use of segments is a detail of the allocator implementation in content/ and
should not exist here.

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

Done.

+
+  // The discardable memory segments will be dumped with
+  // "discardable/segments" as the parent and will be owned by
+  // sub-allocations dumped with kAllocatedObjectsDumpName as their parent.
+  pmd->AddOwnershipEdge(objects_dump->guid(),
+                        discardable_segments_dump->guid());

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

same here. we shouldn't be referring to segments here.

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

Done.

+}
+
 }  // namespace base