Reserve space in the resource ID set.

cc/surfaces/surface_aggregator.cc

Index: cc/surfaces/surface_aggregator.cc
diff --git a/cc/surfaces/surface_aggregator.cc b/cc/surfaces/surface_aggregator.cc
index b4123d01d48c3c376d6f7a19dd2ccd741c4dcab7..7c6f4f74582ba6e758c22b25e9d4b52cae6d6bac 100644
--- a/cc/surfaces/surface_aggregator.cc
+++ b/cc/surfaces/surface_aggregator.cc
@@ -170,6 +170,17 @@ bool SurfaceAggregator::ValidateResources(
   provider_->ReceiveFromChild(child_id, frame_data->resource_list);
 
   ResourceProvider::ResourceIdSet referenced_resources;
+  size_t reserve_size = frame_data->resource_list.size();
+#if defined(COMPILER_MSVC)
+  referenced_resources.reserve(reserve_size);
+#elif defined(COMPILER_GCC)
+  // Pre-standard hash-tables only implement resize, which behaves similarly
+  // to reserve for these keys. Resizing to 0 may also be broken (particularly
+  // on stlport).
+  // TODO(jbauman): Replace with reserve when C++11 is supported everywhere.
+  if (reserve_size)
+    referenced_resources.resize(reserve_size);
+#endif
 
   bool invalid_frame = false;
   DrawQuad::ResourceIteratorCallback remap =