Mojo C++ bindings: Add mojo::Array<T>::reserve()

mojo/public/cpp/bindings/array.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_ARRAY_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_ARRAY_H_
 
 #include <stddef.h>
 #include <string.h>
 #include <algorithm>
@@ skipping 115 matching lines @@
   // Resizes the array to |size| and makes it non-null. Otherwise, works just
   // like the resize method of |std::vector|.
   void resize(size_t size) {
     is_null_ = false;
     vec_.resize(size);
   }
 
   // Sets the array to empty (even if previously it was null.)
   void SetToEmpty() { resize(0); }
 
+  // Ensures the underlying storage can store up to |size| elements without
+  // performing reallocations. This works like the reserve method of
+  // |std::vector|.
+  void reserve(size_t size) { vec_.reserve(size); }
+
   // Returns a const reference to the |std::vector| managed by this class. If
   // the array is null, this will be an empty vector.
   const std::vector<T>& storage() const { return vec_; }
 
   // Passes the underlying storage and resets this array to null.
   std::vector<T> PassStorage() {
     is_null_ = true;
     return std::move(vec_);
   }
 
@@ skipping 124 matching lines @@
   if (a.is_null())
     return !b.is_null();
   if (b.is_null())
     return false;
   return a.storage() < b.storage();
 }
 
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_ARRAY_H_