[WIP] Add SharedMemoryTracker to dump base::SharedMemory usage

gpu/command_buffer/client/mapped_memory.cc

Index: gpu/command_buffer/client/mapped_memory.cc
diff --git a/gpu/command_buffer/client/mapped_memory.cc b/gpu/command_buffer/client/mapped_memory.cc
index 708e121f39c0c24a9593b0714bb14f3b28b5c210..bf6765d5bba142609fe3cf8b49525772494a84fb 100644
--- a/gpu/command_buffer/client/mapped_memory.cc
+++ b/gpu/command_buffer/client/mapped_memory.cc
@@ -13,6 +13,7 @@
 #include "base/atomic_sequence_num.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
+#include "base/memory/shared_memory_tracker.h"
 #include "base/strings/stringprintf.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/trace_event/memory_dump_manager.h"
@@ -186,11 +187,16 @@ bool MappedMemoryManager::OnMemoryDump(
     dump->AddScalar("free_size", MemoryAllocatorDump::kUnitsBytes,
                     chunk->GetFreeSize());
 
-    auto guid = GetBufferGUIDForTracing(tracing_process_id, chunk->shm_id());
+    auto shared_memory = chunk->buffer()->backing()->shared_memory();
+    if (shared_memory) {
+      auto guid = GetBufferGUIDForTracing(tracing_process_id, chunk->shm_id());
 
-    const int kImportance = 2;
-    pmd->CreateSharedGlobalAllocatorDump(guid);
-    pmd->AddOwnershipEdge(dump->guid(), guid, kImportance);
+      const int kImportance = 2;
+      pmd->CreateSharedGlobalAllocatorDump(guid);
+      pmd->AddOwnershipEdge(dump->guid(), guid, kImportance);
+      base::SharedMemoryTracker::AddOwnershipEdgeToSharedGlobalDump(pmd, guid,
+          shared_memory->handle(), shared_memory->mapped_size());
+    }
   }
 
   return true;