Preallocate sample buffer to avoid resizes

src/profiler/sampling-heap-profiler.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/profiler/sampling-heap-profiler.h"
 
 #include <stdint.h>
 #include <memory>
 #include "src/api.h"
 #include "src/base/utils/random-number-generator.h"
@@ skipping 164 matching lines @@
 }
 
 v8::AllocationProfile::Node* SamplingHeapProfiler::TranslateAllocationNode(
     AllocationProfile* profile, SamplingHeapProfiler::AllocationNode* node,
     const std::map<int, Script*>& scripts) {
   Local<v8::String> script_name =
       ToApiHandle<v8::String>(isolate_->factory()->InternalizeUtf8String(""));
   int line = v8::AllocationProfile::kNoLineNumberInfo;
   int column = v8::AllocationProfile::kNoColumnNumberInfo;
   std::vector<v8::AllocationProfile::Allocation> allocations;
+  allocations.reserve(node->allocations_.size());
   if (node->script_id_ != v8::UnboundScript::kNoScriptId) {
     // Cannot use std::map<T>::at because it is not available on android.
     auto non_const_scripts = const_cast<std::map<int, Script*>&>(scripts);
     Script* script = non_const_scripts[node->script_id_];
     if (script->name()->IsName()) {
       Name* name = Name::cast(script->name());
       script_name = ToApiHandle<v8::String>(
           isolate_->factory()->InternalizeUtf8String(names_->GetName(name)));
     }
     Handle<Script> script_handle(script);
@@ skipping 33 matching lines @@
   auto profile = new v8::internal::AllocationProfile();
 
   TranslateAllocationNode(profile, &profile_root_, scripts);
 
   return profile;
 }
 
 
 }  // namespace internal
 }  // namespace v8