[tracing] Introduce support for userland memory allocators dumps.

base/trace_event/process_memory_dump.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/process_memory_dump.h"
 
 #include "base/trace_event/process_memory_totals.h"
 #include "base/trace_event/trace_event_argument.h"
 
 namespace base {
 namespace trace_event {
 
 ProcessMemoryDump::ProcessMemoryDump()
     : has_process_totals_(false), has_process_mmaps_(false) {
 }
 
 ProcessMemoryDump::~ProcessMemoryDump() {
 }
 
+MemoryAllocatorDump* ProcessMemoryDump::AddAllocatorDump(
+    const std::string& name) {
+  return AddAllocatorDump(name, nullptr);
+}
+
+MemoryAllocatorDump* ProcessMemoryDump::AddAllocatorDump(
+    const std::string& name,
+    MemoryAllocatorDump* parent) {
+  DCHECK_EQ(0ul, allocator_dumps_.count(name));
+  MemoryAllocatorDump* mad = new MemoryAllocatorDump(name, parent);
+  allocator_dumps_storage_.push_back(mad);
+  allocator_dumps_[name] = mad;
+  return mad;
+}
+
+MemoryAllocatorDump* ProcessMemoryDump::GetAllocatorDump(
+    const std::string& name) const {
+  auto it = allocator_dumps_.find(name);
+  return it == allocator_dumps_.end() ? nullptr : it->second;
+}
+
 void ProcessMemoryDump::AsValueInto(TracedValue* value) const {
   // Build up the [dumper name] -> [value] dictionary.
   if (has_process_totals_) {
     value->BeginDictionary("process_totals");
     process_totals_.AsValueInto(value);
     value->EndDictionary();
   }
   if (has_process_mmaps_) {
     value->BeginDictionary("process_mmaps");
     process_mmaps_.AsValueInto(value);
     value->EndDictionary();
   }
+  if (allocator_dumps_storage_.size() > 0) {
+    value->BeginDictionary("allocators");
+    for (const MemoryAllocatorDump* allocator_dump : allocator_dumps_storage_)
+      allocator_dump->AsValueInto(value);
+    value->EndDictionary();
+  }
 }
 
 }  // namespace trace_event
 }  // namespace base