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

base/trace_event/trace_event_memory_overhead.h

Index: base/trace_event/trace_event_memory_overhead.h
diff --git a/base/trace_event/trace_event_memory_overhead.h b/base/trace_event/trace_event_memory_overhead.h
index 0d5769bdcd3e7516abeed45cc679947614ce6c34..1587a3099f6adfc35fb5533e3b1852e122c18866 100644
--- a/base/trace_event/trace_event_memory_overhead.h
+++ b/base/trace_event/trace_event_memory_overhead.h
@@ -6,12 +6,11 @@
 #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 {
@@ -26,18 +25,35 @@ 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);
@@ -49,7 +65,7 @@ class BASE_EXPORT TraceEventMemoryOverhead {
   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);
@@ -62,14 +78,12 @@ class BASE_EXPORT TraceEventMemoryOverhead {
     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_;
-
-  void AddOrCreateInternal(const char* object_type,
-                           size_t count,
-                           size_t allocated_size_in_bytes,
-                           size_t resident_size_in_bytes);
+  ObjectCountAndSize allocated_objects_[ObjectType::kLast];
+
+  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);
 };