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

base/memory/shared_memory_tracker.cc

Index: base/memory/shared_memory_tracker.cc
diff --git a/base/memory/shared_memory_tracker.cc b/base/memory/shared_memory_tracker.cc
index 8613f595336ada19357c900cf0ab9bf4d243b7f4..0628a7717137bee78d3162cac8ba73d2eaf5e662 100644
--- a/base/memory/shared_memory_tracker.cc
+++ b/base/memory/shared_memory_tracker.cc
@@ -73,11 +73,9 @@ bool SharedMemoryTracker::OnMemoryDump(const trace_event::MemoryDumpArgs& args,
     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;
 }