[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 7f16a6895c1110b5e63d79bd2242199a5cf50ad3..10a5745f01f63e6797a5cfbc88c97e6ae7e176ed 100644
--- a/base/memory/shared_memory_tracker.cc
+++ b/base/memory/shared_memory_tracker.cc
@@ -89,11 +89,10 @@ bool SharedMemoryTracker::OnMemoryDump(const trace_event::MemoryDumpArgs& args,
         pmd->CreateSharedGlobalAllocatorDump(dump_guid);
     global_dump->AddScalar(trace_event::MemoryAllocatorDump::kNameSize,
                            trace_event::MemoryAllocatorDump::kUnitsBytes, size);
-    // 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 */);

[hajimehoshi, 2017/06/08 05:10:05]

I tend to think we should have ProcessMemoryDump::kDefaultImportance (= 0)
constant value. Actually, one of my CLs will require the same hard-coding so
far. Wdyt?

[ssid, 2017/06/08 18:44:23]

I think the users of edges should be aware of the importance numbers when they
use them. Let's get to the issue about the other client in your cl. Right now I
don't think it's necessary.

   }
   return true;
 }