Change TypeConverter<X,Y>::ConvertFrom and ConvertTo into a single symmetric

mojo/public/cpp/bindings/tests/sample_service_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 <algorithm>
 #include <ostream>
 #include <string>
 
 #include "mojo/public/cpp/environment/environment.h"
 #include "mojo/public/cpp/system/macros.h"
 #include "mojo/public/interfaces/bindings/tests/sample_service.mojom.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace mojo {
 
 template <>
-class TypeConverter<sample::BarPtr, int32_t> {
- public:
-  static int32_t ConvertTo(const sample::BarPtr& bar) {
+struct TypeConverter<int32_t, sample::BarPtr> {
+  static int32_t Convert(const sample::BarPtr& bar) {
     return static_cast<int32_t>(bar->alpha) << 16 |
            static_cast<int32_t>(bar->beta) << 8 |
            static_cast<int32_t>(bar->gamma);
   }
 };
 
 }  // namespace mojo
 
 namespace sample {
 namespace {
@@ skipping 343 matching lines @@
   ASSERT_FALSE(defaults->a22.is_null());
   EXPECT_EQ(imported::SHAPE_RECTANGLE, defaults->a22->shape);
   EXPECT_EQ(imported::COLOR_BLACK, defaults->a22->color);
   EXPECT_EQ(0xFFFFFFFFFFFFFFFFULL, defaults->a23);
   EXPECT_EQ(0x123456789, defaults->a24);
   EXPECT_EQ(-0x123456789, defaults->a25);
 }
 
 }  // namespace
 }  // namespace sample