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

content/child/child_discardable_shared_memory_manager.cc

 // Copyright 2014 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.
 
 #include "content/child/child_discardable_shared_memory_manager.h"
 
 #include "base/atomic_sequence_num.h"
 #include "base/bind.h"
 #include "base/debug/crash_logging.h"
 #include "base/memory/discardable_memory.h"
@@ skipping 174 matching lines @@
     heap_.MergeIntoFreeLists(leftover.Pass());
   }
 
   MemoryUsageChanged(heap_.GetSize(), heap_.GetSizeOfFreeLists());
 
   return make_scoped_ptr(new DiscardableMemoryImpl(this, new_span.Pass()));
 }
 
 bool ChildDiscardableSharedMemoryManager::OnMemoryDump(
     base::trace_event::ProcessMemoryDump* pmd) {
+  // Creates a common dump for all the sub-allocated objects from discardable
+  // memory. To expess any suballocation, the dump providers need to create a
+  // sub-allocation edge from this node.
+  // Eg. : pmd->AddSuballocation(skia_dump_guid,
+  //                             "discardable/allocated_objects");
+  base::trace_event::MemoryAllocatorDump* objects_dump =
+      pmd->CreateAllocatorDump("discardable/allocated_objects");

[petrcermak, 2015/07/29 11:53:34]

Any chance this name could be a constant like
https://code.google.com/p/chromium/codesearch#chromium/src/base/trace_event/m...
?

[ssid, 2015/07/29 16:20:51]

Done.

+  base::trace_event::MemoryAllocatorDump* discardable_segments_dump =
+      pmd->CreateAllocatorDump("discardable/segments");

[petrcermak, 2015/07/29 11:53:34]

Could this be a constant?

[ssid, 2015/07/29 16:20:51]

Done.

+
+  // The discardable memory segments will go under the dump
+  // "discardable/segments" and any sub-allocations under
+  // "discardable/allocated_objects" will be owned by it.

[petrcermak, 2015/07/29 11:53:34]

The relationship is reversed (in the comment).

[ssid, 2015/07/29 16:20:51]

Done.

+  pmd->AddOwnershipEdge(objects_dump->guid(),
+                        discardable_segments_dump->guid());
+
   base::AutoLock lock(lock_);
   return heap_.OnMemoryDump(pmd);
 }
 
 void ChildDiscardableSharedMemoryManager::ReleaseFreeMemory() {
   base::AutoLock lock(lock_);
 
   size_t heap_size_prior_to_releasing_memory = heap_.GetSize();
 
   // Release both purged and free memory.
@@ skipping 85 matching lines @@
       "discardable-memory-allocated";
   base::debug::SetCrashKeyValue(kDiscardableMemoryAllocatedKey,
                                 base::Uint64ToString(new_bytes_total));
 
   static const char kDiscardableMemoryFreeKey[] = "discardable-memory-free";
   base::debug::SetCrashKeyValue(kDiscardableMemoryFreeKey,
                                 base::Uint64ToString(new_bytes_free));
 }
 
 }  // namespace content