mojo: Fix c++ bindings so serialization of empty arrays doesn't crash.

mojo/public/cpp/bindings/tests/array_unittest.cc

 // Copyright 2014 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.
 
 #include "mojo/public/cpp/bindings/array.h"
 #include "mojo/public/cpp/bindings/lib/array_internal.h"
 #include "mojo/public/cpp/bindings/lib/array_serialization.h"
 #include "mojo/public/cpp/bindings/lib/fixed_buffer.h"
 #include "mojo/public/cpp/bindings/tests/container_test_util.h"
 #include "mojo/public/cpp/environment/environment.h"
@@ skipping 153 matching lines @@
       array.Pass(), &buf, &data);
 
   Array<int32_t> array2;
   Deserialize_(data, &array2);
 
   EXPECT_EQ(4U, array2.size());
   for (size_t i = 0; i < array2.size(); ++i)
     EXPECT_EQ(static_cast<int32_t>(i), array2[i]);
 }
 
+TEST_F(ArrayTest, Serialization_EmptyArrayOfPOD) {
+  Array<int32_t> array(0);
+  size_t size = GetSerializedSize_(array);
+  EXPECT_EQ(8U, size);
+
+  FixedBuffer buf(size);
+  Array_Data<int32_t>* data;
+  SerializeArray_<ArrayValidateParams<0, false, NoValidateParams>>(
+      array.Pass(), &buf, &data);
+
+  Array<int32_t> array2;
+  Deserialize_(data, &array2);
+  EXPECT_EQ(0U, array2.size());
+}
+
 TEST_F(ArrayTest, Serialization_ArrayOfArrayOfPOD) {
   Array<Array<int32_t>> array(2);
   for (size_t j = 0; j < array.size(); ++j) {
     Array<int32_t> inner(4);
     for (size_t i = 0; i < inner.size(); ++i)
       inner[i] = static_cast<int32_t>(i + (j * 10));
     array[j] = inner.Pass();
   }
 
   size_t size = GetSerializedSize_(array);
@@ skipping 242 matching lines @@
     EXPECT_TRUE(array[i].moved());
     EXPECT_EQ(value_ptrs[i], array[i].ptr());
   }
   array.reset();
   EXPECT_EQ(0u, MoveOnlyType::num_instances());
 }
 
 }  // namespace
 }  // namespace test
 }  // namespace mojo