[Tracing] Remove unnecessary memory allocation in runtime call stats.

src/tracing/trace-event.cc

 // Copyright 2015 the V8 project 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 "src/tracing/trace-event.h"
 
 #include <string.h>
 
 #include "src/counters.h"
 #include "src/isolate.h"
@@ skipping 10 matching lines @@
 v8::Platform* TraceEventHelper::GetCurrentPlatform() {
   return v8::internal::V8::GetCurrentPlatform();
 }
 
 void CallStatsScopedTracer::AddEndTraceEvent() {
   if (!has_parent_scope_ && p_data_->isolate) {
     v8::internal::tracing::AddTraceEvent(
         TRACE_EVENT_PHASE_END, p_data_->category_group_enabled, p_data_->name,
         v8::internal::tracing::kGlobalScope, v8::internal::tracing::kNoId,
         v8::internal::tracing::kNoId, TRACE_EVENT_FLAG_NONE,
-        "runtime-call-stats",
-        TRACE_STR_COPY(
-            p_data_->isolate->counters()->runtime_call_stats()->Dump()));
+        "runtime-call-stats", TRACE_STR_COPY(p_data_->isolate->counters()
+                                                 ->runtime_call_stats()
+                                                 ->Dump()
+                                                 .c_str()));
   } else {
     v8::internal::tracing::AddTraceEvent(
         TRACE_EVENT_PHASE_END, p_data_->category_group_enabled, p_data_->name,
         v8::internal::tracing::kGlobalScope, v8::internal::tracing::kNoId,
         v8::internal::tracing::kNoId, TRACE_EVENT_FLAG_NONE);
   }
 }
 
 void CallStatsScopedTracer::Initialize(v8::internal::Isolate* isolate,
                                        const uint8_t* category_group_enabled,
                                        const char* name) {
   data_.isolate = isolate;
   data_.category_group_enabled = category_group_enabled;
   data_.name = name;
   p_data_ = &data_;
   RuntimeCallStats* table = isolate->counters()->runtime_call_stats();
   has_parent_scope_ = table->InUse();
   if (!has_parent_scope_) table->Reset();
   v8::internal::tracing::AddTraceEvent(
       TRACE_EVENT_PHASE_BEGIN, category_group_enabled, name,
       v8::internal::tracing::kGlobalScope, v8::internal::tracing::kNoId,
       TRACE_EVENT_FLAG_NONE, v8::internal::tracing::kNoId);
 }
 
 }  // namespace tracing
 }  // namespace internal
 }  // namespace v8