Update from https://crrev.com/316786

base/trace_event/memory_dump_manager.cc

+// Copyright 2015 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/trace_event/memory_dump_manager.h"
+
+#include <algorithm>
+
+#include "base/compiler_specific.h"
+#include "base/trace_event/memory_dump_provider.h"
+#include "base/trace_event/process_memory_dump.h"
+
+// TODO(primiano): in a separate CL rename DeleteTraceLogForTesting into
+// something like base::internal::TeardownSingletonForTesting so we don't have
+// to add a new friend to singleton each time.
+class DeleteTraceLogForTesting {
+ public:
+  static void Delete() {
+    Singleton<
+        base::trace_event::MemoryDumpManager,
+        LeakySingletonTraits<base::trace_event::MemoryDumpManager>>::OnExit(0);
+  }
+};
+
+namespace base {
+namespace trace_event {
+
+// TODO(primiano): this should be smarter and should do something similar to
+// trace event synthetic delays.
+const char MemoryDumpManager::kTraceCategory[] =
+    TRACE_DISABLED_BY_DEFAULT("memory-dumps");
+
+// static
+MemoryDumpManager* MemoryDumpManager::GetInstance() {
+  return Singleton<MemoryDumpManager,
+                   LeakySingletonTraits<MemoryDumpManager>>::get();
+}
+
+// static
+void MemoryDumpManager::DeleteForTesting() {
+  DeleteTraceLogForTesting::Delete();
+}
+
+MemoryDumpManager::MemoryDumpManager() : memory_tracing_enabled_(0) {
+}
+
+MemoryDumpManager::~MemoryDumpManager() {
+  base::trace_event::TraceLog::GetInstance()->RemoveEnabledStateObserver(this);
+}
+
+void MemoryDumpManager::Initialize() {
+  TRACE_EVENT0(kTraceCategory, "init");  // Add to trace-viewer category list.
+  trace_event::TraceLog::GetInstance()->AddEnabledStateObserver(this);
+}
+
+void MemoryDumpManager::RegisterDumpProvider(MemoryDumpProvider* mdp) {
+  AutoLock lock(lock_);
+  if (std::find(dump_providers_registered_.begin(),
+                dump_providers_registered_.end(),
+                mdp) != dump_providers_registered_.end()) {
+    return;
+  }
+  dump_providers_registered_.push_back(mdp);
+}
+
+void MemoryDumpManager::UnregisterDumpProvider(MemoryDumpProvider* mdp) {
+  AutoLock lock(lock_);
+
+  // Remove from the registered providers list.
+  auto it = std::find(dump_providers_registered_.begin(),
+                      dump_providers_registered_.end(), mdp);
+  if (it != dump_providers_registered_.end())
+    dump_providers_registered_.erase(it);
+
+  // Remove from the enabled providers list. This is to deal with the case that
+  // UnregisterDumpProvider is called while the trace is enabled.
+  it = std::find(dump_providers_enabled_.begin(), dump_providers_enabled_.end(),
+                 mdp);
+  if (it != dump_providers_enabled_.end())
+    dump_providers_enabled_.erase(it);
+}
+
+void MemoryDumpManager::RequestDumpPoint(DumpPointType type) {
+  // TODO(primiano): this will have more logic, IPC broadcast & co.
+  // Bail out immediately if tracing is not enabled at all.
+  if (!UNLIKELY(subtle::NoBarrier_Load(&memory_tracing_enabled_)))
+    return;
+
+  CreateLocalDumpPoint();
+}
+
+void MemoryDumpManager::BroadcastDumpRequest() {
+  NOTREACHED();  // TODO(primiano): implement IPC synchronization.
+}
+
+// Creates a dump point for the current process and appends it to the trace.
+void MemoryDumpManager::CreateLocalDumpPoint() {
+  AutoLock lock(lock_);
+  // TRACE_EVENT_* macros don't induce scoped_refptr type inference, hence we
+  // need the base ConvertableToTraceFormat and the upcast below. The
+  // alternative would be unnecessarily expensive (double Acquire/Release).
+  scoped_refptr<ConvertableToTraceFormat> pmd(new ProcessMemoryDump());
+
+  for (MemoryDumpProvider* dump_provider : dump_providers_enabled_) {
+    dump_provider->DumpInto(static_cast<ProcessMemoryDump*>(pmd.get()));
+  }
+
+  // TODO(primiano): add the dump point to the trace at this point.
+}
+
+void MemoryDumpManager::OnTraceLogEnabled() {
+  // TODO(primiano): at this point we query  TraceLog::GetCurrentCategoryFilter
+  // to figure out (and cache) which dumpers should be enabled or not.
+  // For the moment piggy back everything on the generic "memory" category.
+  bool enabled;
+  TRACE_EVENT_CATEGORY_GROUP_ENABLED(kTraceCategory, &enabled);
+
+  AutoLock lock(lock_);
+  if (enabled) {
+    dump_providers_enabled_.assign(dump_providers_registered_.begin(),
+                                   dump_providers_registered_.end());
+  } else {
+    dump_providers_enabled_.clear();
+  }
+  subtle::NoBarrier_Store(&memory_tracing_enabled_, 1);
+}
+
+void MemoryDumpManager::OnTraceLogDisabled() {
+  AutoLock lock(lock_);
+  dump_providers_enabled_.clear();
+  subtle::NoBarrier_Store(&memory_tracing_enabled_, 0);
+}
+
+}  // namespace trace_event
+}  // namespace base