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

base/trace_event/trace_event_impl.cc

 // 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.
 
 #include "base/trace_event/trace_event_impl.h"
 
 #include "base/format_macros.h"
 #include "base/json/string_escape.h"
 #include "base/stl_util.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 153 matching lines @@
   }
 }
 
 void TraceEvent::Reset() {
   // Only reset fields that won't be initialized in Initialize(), or that may
   // hold references to other objects.
   duration_ = TimeDelta::FromInternalValue(-1);
   parameter_copy_storage_ = NULL;
   for (int i = 0; i < kTraceMaxNumArgs; ++i)
     convertable_values_[i] = NULL;
-  cached_memory_overhead_estimate_.reset();
 }
 
 void TraceEvent::UpdateDuration(const TraceTicks& now,
                                 const ThreadTicks& thread_now) {
   DCHECK_EQ(duration_.ToInternalValue(), -1);
   duration_ = now - timestamp_;
   thread_duration_ = thread_now - thread_timestamp_;
 }
 
 void TraceEvent::EstimateTraceMemoryOverhead(
     TraceEventMemoryOverhead* overhead) {
-  if (!cached_memory_overhead_estimate_) {
-    cached_memory_overhead_estimate_.reset(new TraceEventMemoryOverhead);
-    cached_memory_overhead_estimate_->Add("TraceEvent", sizeof(*this));
-    // TODO(primiano): parameter_copy_storage_ is refcounted and, in theory,
-    // could be shared by several events and we might overcount. In practice
-    // this is unlikely but it's worth checking.
-    if (parameter_copy_storage_) {
-      cached_memory_overhead_estimate_->AddRefCountedString(
-          *parameter_copy_storage_.get());
-    }
-    for (size_t i = 0; i < kTraceMaxNumArgs; ++i) {
-      if (arg_types_[i] == TRACE_VALUE_TYPE_CONVERTABLE) {
-        convertable_values_[i]->EstimateTraceMemoryOverhead(
-            cached_memory_overhead_estimate_.get());
-      }
-    }
-    cached_memory_overhead_estimate_->AddSelf();
+  overhead->Add("TraceEvent", sizeof(*this));
+
+  // TODO(primiano): parameter_copy_storage_ is refcounted and, in theory,
+  // could be shared by several events and we might overcount. In practice
+  // this is unlikely but it's worth checking.
+  if (parameter_copy_storage_)
+    overhead->AddRefCountedString(*parameter_copy_storage_.get());
+
+  for (size_t i = 0; i < kTraceMaxNumArgs; ++i) {
+    if (arg_types_[i] == TRACE_VALUE_TYPE_CONVERTABLE)
+      convertable_values_[i]->EstimateTraceMemoryOverhead(overhead);
   }
-  overhead->Update(*cached_memory_overhead_estimate_);
 }
 
 // static
 void TraceEvent::AppendValueAsJSON(unsigned char type,
                                    TraceEvent::TraceValue value,
                                    std::string* out) {
   switch (type) {
     case TRACE_VALUE_TYPE_BOOL:
       *out += value.as_bool ? "true" : "false";
       break;
@@ skipping 181 matching lines @@
         AppendValueAsJSON(arg_types_[i], arg_values_[i], &value_as_text);
 
       *out << value_as_text;
     }
     *out << "}";
   }
 }
 
 }  // namespace trace_event
 }  // namespace base