Replace use of std::unique_ptr<T> with T* for AST nodes

This is a minimal effort to fix up the code. There's substantial code
cleanup which can now be done, which is done in the next change.

Bug: tint:322
Change-Id: Iafcf5e814837d9534889e8c21333de4931a19cfa
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/32864
Commit-Queue: dan sinclair <dsinclair@chromium.org>
Reviewed-by: dan sinclair <dsinclair@chromium.org>
diff --git a/src/ast/scalar_constructor_expression.cc b/src/ast/scalar_constructor_expression.cc
index 52b3ed2..f82983d 100644
--- a/src/ast/scalar_constructor_expression.cc
+++ b/src/ast/scalar_constructor_expression.cc
@@ -20,14 +20,12 @@
 ScalarConstructorExpression::ScalarConstructorExpression()
     : ConstructorExpression() {}
 
-ScalarConstructorExpression::ScalarConstructorExpression(
-    std::unique_ptr<Literal> literal)
-    : ConstructorExpression(), literal_(std::move(literal)) {}
+ScalarConstructorExpression::ScalarConstructorExpression(Literal* literal)
+    : literal_(literal) {}
 
-ScalarConstructorExpression::ScalarConstructorExpression(
-    const Source& source,
-    std::unique_ptr<Literal> litearl)
-    : ConstructorExpression(source), literal_(std::move(litearl)) {}
+ScalarConstructorExpression::ScalarConstructorExpression(const Source& source,
+                                                         Literal* litearl)
+    : ConstructorExpression(source), literal_(litearl) {}
 
 ScalarConstructorExpression::ScalarConstructorExpression(
     ScalarConstructorExpression&&) = default;