Remove most usage of Vector

sky/engine/tonic/dart_snapshot_loader.cc

Index: sky/engine/tonic/dart_snapshot_loader.cc
diff --git a/sky/engine/tonic/dart_snapshot_loader.cc b/sky/engine/tonic/dart_snapshot_loader.cc
index 04b4de01a75836aae57d531a1bf2a8e72a9c3a35..9277da7ff01b141bbce088eb817c39de8b4c34e0 100644
--- a/sky/engine/tonic/dart_snapshot_loader.cc
+++ b/sky/engine/tonic/dart_snapshot_loader.cc
@@ -32,7 +32,8 @@ void DartSnapshotLoader::LoadSnapshot(mojo::ScopedDataPipeConsumerHandle pipe,
 }
 
 void DartSnapshotLoader::OnDataAvailable(const void* data, size_t num_bytes) {
-  buffer_.append(static_cast<const uint8_t*>(data), num_bytes);
+  const uint8_t* bytes = static_cast<const uint8_t*>(data);
+  buffer_.insert(buffer_.end(), bytes, bytes + num_bytes);
 }
 
 void DartSnapshotLoader::OnDataComplete() {