resolver: Delay copy of TemplateState

Shows up in profiling, and doesn't always need to be done.

Change-Id: If8bf061563979d17dea4c48334dab4834770d921
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/116865
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Auto-Submit: Ben Clayton <bclayton@google.com>

src/tint/resolver/intrinsic_table.cc

@@ -1154,7 +1154,7 @@ class Impl : public IntrinsicTable {
     Candidate ScoreOverload(const OverloadInfo* overload,
                             utils::VectorRef<const type::Type*> args,
                             sem::EvaluationStage earliest_eval_stage,
-                            TemplateState templates) const;
+                            const TemplateState& templates) const;
 
     /// Performs overload resolution given the list of candidates, by ranking the conversions of
     /// arguments to the each of the candidate's parameter types.
@@ -1560,7 +1560,7 @@ IntrinsicPrototype Impl::MatchIntrinsic(const IntrinsicInfo& intrinsic,
 Impl::Candidate Impl::ScoreOverload(const OverloadInfo* overload,
                                     utils::VectorRef<const type::Type*> args,
                                     sem::EvaluationStage earliest_eval_stage,
-                                    TemplateState templates) const {
+                                    const TemplateState& in_templates) const {
     // Penalty weights for overload mismatching.
     // This scoring is used to order the suggested overloads in diagnostic on overload mismatch, and
     // has no impact for a correct program.
@@ -1580,6 +1580,10 @@ Impl::Candidate Impl::ScoreOverload(const OverloadInfo* overload,
                                                  std::min(num_parameters, num_arguments));
     }
 
+    // Make a mutable copy of the input templates so we can implicitly match more templated
+    // arguments.
+    TemplateState templates(in_templates);
+
     // Invoke the matchers for each parameter <-> argument pair.
     // If any arguments cannot be matched, then `score` will be increased.
     // If the overload has any template types or numbers then these will be set based on the