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

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..7d38ada032aafe39edfad21b04b64610c3c3459a 100644
--- a/base/memory/shared_memory_tracker.cc
+++ b/base/memory/shared_memory_tracker.cc
@@ -4,40 +4,36 @@
 
 #include "base/memory/shared_memory_tracker.h"
 
-#include "base/memory/shared_memory.h"
+#include "base/format_macros.h"
 #include "base/strings/stringprintf.h"
 #include "base/trace_event/memory_dump_manager.h"
 #include "base/trace_event/process_memory_dump.h"
 
 namespace base {
 
-SharedMemoryTracker::Usage::Usage() = default;
-
-SharedMemoryTracker::Usage::Usage(const Usage& rhs) = default;
-
-SharedMemoryTracker::Usage::~Usage() = default;
-
 // static
 SharedMemoryTracker* SharedMemoryTracker::GetInstance() {
   static SharedMemoryTracker* instance = new SharedMemoryTracker;
   return instance;
 }
 
+// static
+bool SharedMemoryTracker::AddOwnershipEdges(
+    trace_event::ProcessMemoryDump* pmd,
+    const trace_event::MemoryAllocatorDumpGuid& source,
+    const SharedMemory& shared_memory) {
+  std::string id_str = shared_memory.handle().GetGUIDNameForTracing();
+  // The same dump name might be already created on single-process mode.
+  trace_event::MemoryAllocatorDump* dump =
+      pmd->GetOrCreateAllocatorDump(id_str);
+  pmd->AddOwnershipEdge(source, dump->guid());
+  return true;
+}
+
 void SharedMemoryTracker::IncrementMemoryUsage(
     const SharedMemory& shared_memory) {
-  Usage usage;
-  // |shared_memory|'s unique ID must be generated here and it'd be too late at
-  // OnMemoryDump. An ID is generated with a SharedMemoryHandle, but the handle
-  // might already be closed at that time. Now IncrementMemoryUsage is called
-  // just after mmap and the handle must live then. See the discussion at
-  // crbug.com/604726#c30.
-  SharedMemory::UniqueId id;
-  if (!shared_memory.GetUniqueId(&id))
-    return;
-  usage.unique_id = id;
-  usage.size = shared_memory.mapped_size();
   AutoLock hold(usages_lock_);
-  usages_[&shared_memory] = usage;
+  usages_[&shared_memory] = shared_memory.mapped_size();
 }
 
 void SharedMemoryTracker::DecrementMemoryUsage(
@@ -48,36 +44,30 @@ void SharedMemoryTracker::DecrementMemoryUsage(
 
 bool SharedMemoryTracker::OnMemoryDump(const trace_event::MemoryDumpArgs& args,
                                        trace_event::ProcessMemoryDump* pmd) {
-  std::unordered_map<SharedMemory::UniqueId, size_t, SharedMemory::UniqueIdHash>
-      sizes;
-  {
-    AutoLock hold(usages_lock_);
-    for (const auto& usage : usages_)
-      sizes[usage.second.unique_id] += usage.second.size;
-  }
-  for (auto& size : sizes) {
-    const SharedMemory::UniqueId& id = size.first;
-    std::string dump_name = StringPrintf("%s/%lld.%lld", "shared_memory",
-                                         static_cast<long long>(id.first),
-                                         static_cast<long long>(id.second));
-    auto guid = trace_event::MemoryAllocatorDumpGuid(dump_name);
+  for (auto& usage : usages_) {
+    const SharedMemory* shared_memory = usage.first;
+    std::string dump_name = shared_memory->handle().GetGUIDNameForTracing();
+    if (dump_name.empty())
+      continue;
     trace_event::MemoryAllocatorDump* local_dump =
-        pmd->CreateAllocatorDump(dump_name);
+        pmd->GetOrCreateAllocatorDump(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.second);
+                          usage.second);
+    auto guid = trace_event::MemoryAllocatorDumpGuid(dump_name);
     trace_event::MemoryAllocatorDump* global_dump =
         pmd->CreateSharedGlobalAllocatorDump(guid);
     global_dump->AddScalar(trace_event::MemoryAllocatorDump::kNameSize,
                            trace_event::MemoryAllocatorDump::kUnitsBytes,
-                           size.second);
+                           usage.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());
+    pmd->AddOwnershipEdge(local_dump->guid(), global_dump->guid(),
+                          shared_memory->importance());
   }
   return true;
 }