Preallocate sample buffer to avoid resizes

R=ofrobots@google.com
BUG=

Review URL: https://codereview.chromium.org/1712893002

Cr-Commit-Position: refs/heads/master@{#34161}

src/profiler/sampling-heap-profiler.cc

@@ -182,6 +182,7 @@ v8::AllocationProfile::Node* SamplingHeapProfiler::TranslateAllocationNode(
   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);