Remove `SymbolTable::NameFor`

This CL removes the `NameFor` method from SymbolTable and accesses the
symbols name directly.

Change-Id: Ic4ad6eecfa78efb946d97aeaecf2d784af2e6f16
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/127301
Reviewed-by: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Dan Sinclair <dsinclair@chromium.org>
diff --git a/src/tint/ast/bitcast_expression_test.cc b/src/tint/ast/bitcast_expression_test.cc
index d288a77..ce4ab1d 100644
--- a/src/tint/ast/bitcast_expression_test.cc
+++ b/src/tint/ast/bitcast_expression_test.cc
@@ -25,7 +25,7 @@
 TEST_F(BitcastExpressionTest, Create) {
     auto* expr = Expr("expr");
     auto* exp = Bitcast(ty.f32(), expr);
-    CheckIdentifier(Symbols(), exp->type, "f32");
+    CheckIdentifier(exp->type, "f32");
     ASSERT_EQ(exp->expr, expr);
 }