[utils] Fix construction of constant OwnedVector

I hit this issue in an unrelated CL and it took me a while to figure out
what's happening.
This CL will allow the creation of constant OwnedVectors via
{OwnedVector<const T>::Of(collection)}.

R=tebbi@chromium.org

Change-Id: I337077a6c3960a2a2a8d857bec7450f664b87a3b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2010109Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65868}

src/utils/vector.h

@@ -195,7 +195,7 @@ class OwnedVector {
   // Allocates a new vector of the specified size via the default allocator.
   static OwnedVector<T> New(size_t size) {
     if (size == 0) return {};
-    return OwnedVector<T>(std::unique_ptr<T[]>(new T[size]), size);
+    return OwnedVector<T>(std::make_unique<T[]>(size), size);
   }
 
   // Allocates a new vector containing the specified collection of values.
@@ -207,7 +207,8 @@ class OwnedVector {
   static OwnedVector<T> Of(const U& collection) {
     Iterator begin = std::begin(collection);
     Iterator end = std::end(collection);
-    OwnedVector<T> vec = New(std::distance(begin, end));
+    using non_const_t = typename std::remove_const<T>::type;
+    auto vec = OwnedVector<non_const_t>::New(std::distance(begin, end));
     std::copy(begin, end, vec.start());
     return vec;
   }

test/unittests/utils/vector-unittest.cc

@@ -57,5 +57,21 @@ TEST(VectorTest, Equals) {
   CHECK(vec3_char != vec1_const_char);
 }
 
+TEST(OwnedVectorConstruction, Equals) {
+  auto int_vec = OwnedVector<int>::New(4);
+  CHECK_EQ(4, int_vec.size());
+  auto find_non_zero = [](int i) { return i != 0; };
+  CHECK_EQ(int_vec.end(),
+           std::find_if(int_vec.begin(), int_vec.end(), find_non_zero));
+
+  constexpr int kInit[] = {4, 11, 3};
+  auto init_vec1 = OwnedVector<int>::Of(kInit);
+  // Note: {const int} should also work: We initialize the owned vector, but
+  // afterwards it's non-modifyable.
+  auto init_vec2 = OwnedVector<const int>::Of(ArrayVector(kInit));
+  CHECK_EQ(init_vec1.as_vector(), ArrayVector(kInit));
+  CHECK_EQ(init_vec1.as_vector(), init_vec2.as_vector());
+}
+
 }  // namespace internal
 }  // namespace v8