Replace remaining std::make_unique<T> -> create<T> for ast::Nodes

create() is currently just a simple forwarder to std::make_unique<>, but
will be later replaced with a function that returns a raw pointer,
and owned by the context.

Bug: tint:322
Change-Id: I9d85e925538789d9b58f32c2bba32a05e22aea1c
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/32863
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: dan sinclair <dsinclair@chromium.org>

src/ast/builder.cc

@@ -26,7 +26,7 @@ Builder::~Builder() = default;
 std::unique_ptr<ast::Variable> Builder::make_var(const std::string& name,
                                                  ast::StorageClass storage,
                                                  ast::type::Type* type) {
-  auto var = std::make_unique<ast::Variable>(name, storage, type);
+  auto var = create<ast::Variable>(name, storage, type);
   return var;
 }
 

src/writer/spirv/builder_if_test.cc

@@ -618,12 +618,12 @@ TEST_F(BuilderTest, If_WithLoad_Bug327) {
   // }
 
   ast::type::BoolType bool_type;
-  auto var = std::make_unique<ast::Variable>("a", ast::StorageClass::kFunction,
-                                             &bool_type);
+  auto var =
+      create<ast::Variable>("a", ast::StorageClass::kFunction, &bool_type);
   td.RegisterVariableForTesting(var.get());
 
-  ast::IfStatement expr(std::make_unique<ast::IdentifierExpression>("a"),
-                        std::make_unique<ast::BlockStatement>());
+  ast::IfStatement expr(create<ast::IdentifierExpression>("a"),
+                        create<ast::BlockStatement>());
 
   ASSERT_TRUE(td.DetermineResultType(&expr)) << td.error();