[tracing] Fix, simplify and speed up accounting of TraceEvent memory overhead

base/trace_event/trace_event_impl.h

 // Copyright (c) 2012 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_IMPL_H_
 #define BASE_TRACE_EVENT_TRACE_EVENT_IMPL_H_
 
 #include <stack>
 #include <string>
@@ skipping 158 matching lines @@
 #endif
 
  private:
   // Note: these are ordered by size (largest first) for optimal packing.
   TraceTicks timestamp_;
   ThreadTicks thread_timestamp_;
   TimeDelta duration_;
   TimeDelta thread_duration_;
   // id_ can be used to store phase-specific data.
   unsigned long long id_;
-  scoped_ptr<TraceEventMemoryOverhead> cached_memory_overhead_estimate_;
   // context_id_ is used to store context information.
   unsigned long long context_id_;
   TraceValue arg_values_[kTraceMaxNumArgs];
   const char* arg_names_[kTraceMaxNumArgs];
   scoped_refptr<ConvertableToTraceFormat> convertable_values_[kTraceMaxNumArgs];
   const unsigned char* category_group_enabled_;
   const char* name_;
   scoped_refptr<base::RefCountedString> parameter_copy_storage_;
   int thread_id_;
   char phase_;
@@ skipping 27 matching lines @@
   }
 
   scoped_ptr<TraceBufferChunk> Clone() const;
 
   void EstimateTraceMemoryOverhead(TraceEventMemoryOverhead* overhead);
 
   static const size_t kTraceBufferChunkSize = 64;
 
  private:
   size_t next_free_;
-  scoped_ptr<TraceEventMemoryOverhead> cached_overhead_estimate_when_full_;
+  scoped_ptr<TraceEventMemoryOverhead> cached_overhead_estimate_;
   TraceEvent chunk_[kTraceBufferChunkSize];
   uint32 seq_;
 };
 
 // TraceBuffer holds the events as they are collected.
 class BASE_EXPORT TraceBuffer {
  public:
   virtual ~TraceBuffer() {}
 
   virtual scoped_ptr<TraceBufferChunk> GetChunk(size_t *index) = 0;
@@ skipping 487 matching lines @@
   subtle::AtomicWord generation_;
   bool use_worker_thread_;
 
   DISALLOW_COPY_AND_ASSIGN(TraceLog);
 };
 
 }  // namespace trace_event
 }  // namespace base
 
 #endif  // BASE_TRACE_EVENT_TRACE_EVENT_IMPL_H_