[memory-infra] Add API to ProcessMemoryDump to create ownership edges for base::SharedMemory

base/memory/shared_memory_tracker.cc

 // Copyright 2017 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 "base/memory/shared_memory_tracker.h"
 
 #include "base/memory/shared_memory.h"
 #include "base/strings/stringprintf.h"
 #include "base/trace_event/memory_dump_manager.h"
 #include "base/trace_event/process_memory_dump.h"
@@ skipping 55 matching lines @@
     // TODO(hajimehoshi): The size is not resident size but virtual size so far.
     // Fix this to record resident size.
     local_dump->AddScalar(trace_event::MemoryAllocatorDump::kNameSize,
                           trace_event::MemoryAllocatorDump::kUnitsBytes,
                           size.second);
     trace_event::MemoryAllocatorDump* global_dump =
         pmd->CreateSharedGlobalAllocatorDump(guid);
     global_dump->AddScalar(trace_event::MemoryAllocatorDump::kNameSize,
                            trace_event::MemoryAllocatorDump::kUnitsBytes,
                            size.second);
-    // TOOD(hajimehoshi): Detect which the shared memory comes from browser,
-    // renderer or GPU process.
-    // TODO(hajimehoshi): Shared memory reported by GPU and discardable is
-    // currently double-counted. Add ownership edges to avoid this.
-    pmd->AddOwnershipEdge(local_dump->guid(), global_dump->guid());
+    // The edges will be overriden by the clients with correct importance.
+    pmd->AddOverridableOwnershipEdge(local_dump->guid(), global_dump->guid(),
+                                     0 /* importance */);
   }
   return true;
 }
 
 SharedMemoryTracker::SharedMemoryTracker() {
   trace_event::MemoryDumpManager::GetInstance()->RegisterDumpProvider(
       this, "SharedMemoryTracker", nullptr);
 }
 
 SharedMemoryTracker::~SharedMemoryTracker() = default;
 
 }  // namespace