tracing: Simplify TraceEventMemoryOverhead, use an enum insted of a map

base/trace_event/heap_profiler_allocation_register.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/heap_profiler_allocation_register.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "base/trace_event/trace_event_memory_overhead.h"
@@ skipping 140 matching lines @@
 AllocationRegister::ConstIterator AllocationRegister::end() const {
   return ConstIterator(*this, AllocationMap::kInvalidKVIndex);
 }
 
 void AllocationRegister::EstimateTraceMemoryOverhead(
     TraceEventMemoryOverhead* overhead) const {
   size_t allocated = sizeof(AllocationRegister);
   size_t resident = sizeof(AllocationRegister) +
                     allocations_.EstimateUsedMemory() +
                     backtraces_.EstimateUsedMemory();
-  overhead->Add("AllocationRegister", allocated, resident);
+  overhead->Add(TraceEventMemoryOverhead::kHeapProfilerAllocationRegister,
+                allocated, resident);
 }
 
 AllocationRegister::BacktraceMap::KVIndex AllocationRegister::InsertBacktrace(
     const Backtrace& backtrace) {
   auto index = backtraces_.Insert(backtrace, 0).first;
   if (index == BacktraceMap::kInvalidKVIndex)
     return kOutOfStorageBacktraceIndex;
   auto& backtrace_and_count = backtraces_.Get(index);
   backtrace_and_count.second++;
   return index;
@@ skipping 13 matching lines @@
   const auto& address_and_info = allocations_.Get(index);
   const auto& backtrace_and_count =
       backtraces_.Get(address_and_info.second.backtrace_index);
   return {address_and_info.first, address_and_info.second.size,
           AllocationContext(backtrace_and_count.first,
                             address_and_info.second.type_name)};
 }
 
 }  // namespace trace_event
 }  // namespace base