[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/string_number_conversions.h"
 #include "base/trace_event/memory_allocator_dump_guid.h"
 #include "base/trace_event/memory_dump_manager.h"
@@ skipping 71 matching lines @@
     trace_event::MemoryAllocatorDump* local_dump =
         pmd->CreateAllocatorDump(dump_name);
     // 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);
     trace_event::MemoryAllocatorDump* global_dump =
         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;
 }
 
 SharedMemoryTracker::SharedMemoryTracker() {
   trace_event::MemoryDumpManager::GetInstance()->RegisterDumpProvider(
       this, "SharedMemoryTracker", nullptr);
 }
 
 SharedMemoryTracker::~SharedMemoryTracker() = default;
 
 }  // namespace