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

base/trace_event/trace_event_memory_overhead.h

 // 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.
 
 #ifndef BASE_TRACE_EVENT_TRACE_EVENT_MEMORY_OVERHEAD_H_
 #define BASE_TRACE_EVENT_TRACE_EVENT_MEMORY_OVERHEAD_H_
 
 #include <stddef.h>
+#include <stdint.h>
 
 #include <unordered_map>
 
 #include "base/base_export.h"
-#include "base/containers/hash_tables.h"
-#include "base/containers/small_map.h"
 #include "base/macros.h"
 
 namespace base {
 
 class RefCountedString;
 class Value;
 
 namespace trace_event {
 
 class ProcessMemoryDump;
 
 // Used to estimate the memory overhead of the tracing infrastructure.
 class BASE_EXPORT TraceEventMemoryOverhead {
  public:
+  enum ObjectType : uint32_t {
+    kOther = 0,
+    kTraceBuffer,
+    kTraceBufferChunk,
+    kTraceEvent,
+    kUnusedTraceEvent,
+    kTracedValue,
+    kConvertableToTraceFormat,
+    kHeapProfilerAllocationRegister,
+    kHeapProfilerTypeNameDeduplicator,
+    kHeapProfilerStackFrameDeduplicator,
+    kStdString,
+    kBaseValue,
+    kTraceEventMemoryOverhead,
+    kLast
+  };
+
   TraceEventMemoryOverhead();
   ~TraceEventMemoryOverhead();
 
   // Use this method to account the overhead of an object for which an estimate
   // is known for both the allocated and resident memory.
-  void Add(const char* object_type,
+  void Add(ObjectType object_type,
            size_t allocated_size_in_bytes,
            size_t resident_size_in_bytes);
 
   // Similar to Add() above, but assumes that
   // |resident_size_in_bytes| == |allocated_size_in_bytes|.
-  void Add(const char* object_type, size_t allocated_size_in_bytes);
+  void Add(ObjectType object_type, size_t allocated_size_in_bytes);
 
   // Specialized profiling functions for commonly used object types.
   void AddString(const std::string& str);
   void AddValue(const Value& value);
   void AddRefCountedString(const RefCountedString& str);
 
   // Call this after all the Add* methods above to account the memory used by
   // this TraceEventMemoryOverhead instance itself.
   void AddSelf();
 
   // Retrieves the count, that is, the count of Add*(|object_type|, ...) calls.
-  size_t GetCount(const char* object_type) const;
+  size_t GetCount(ObjectType object_type) const;
 
   // Adds up and merges all the values from |other| to this instance.
   void Update(const TraceEventMemoryOverhead& other);
 
   void DumpInto(const char* base_name, ProcessMemoryDump* pmd) const;
 
  private:
   struct ObjectCountAndSize {
     size_t count;
     size_t allocated_size_in_bytes;
     size_t resident_size_in_bytes;
   };
-  using map_type =
-      small_map<std::unordered_map<const char*, ObjectCountAndSize>, 16>;
-  map_type allocated_objects_;
+  ObjectCountAndSize allocated_objects_[ObjectType::kLast];
 
-  void AddOrCreateInternal(const char* object_type,
-                           size_t count,
-                           size_t allocated_size_in_bytes,
-                           size_t resident_size_in_bytes);
+  void AddInternal(ObjectType object_type,
+                   size_t count,
+                   size_t allocated_size_in_bytes,
+                   size_t resident_size_in_bytes);
 
   DISALLOW_COPY_AND_ASSIGN(TraceEventMemoryOverhead);
 };
 
 }  // namespace trace_event
 }  // namespace base
 
 #endif  // BASE_TRACE_EVENT_TRACE_EVENT_MEMORY_OVERHEAD_H_