[turbofan] Add support for accessing Uint8ClampedArrays.

src/compiler/typed-optimization.cc

Index: src/compiler/typed-optimization.cc
diff --git a/src/compiler/typed-optimization.cc b/src/compiler/typed-optimization.cc
index 42d5232d589555d27c57ba7969db95dc8e57f5d2..5ebc390c8bc6a1d5f2c7bc3807211ebb88dba30c 100644
--- a/src/compiler/typed-optimization.cc
+++ b/src/compiler/typed-optimization.cc
@@ -87,6 +87,8 @@ Reduction TypedOptimization::Reduce(Node* node) {
     case IrOpcode::kNumberRound:
     case IrOpcode::kNumberTrunc:
       return ReduceNumberRoundop(node);
+    case IrOpcode::kNumberToUint8Clamped:
+      return ReduceNumberToUint8Clamped(node);
     case IrOpcode::kPhi:
       return ReducePhi(node);
     case IrOpcode::kSelect:
@@ -192,6 +194,15 @@ Reduction TypedOptimization::ReduceNumberRoundop(Node* node) {
   return NoChange();
 }
 
+Reduction TypedOptimization::ReduceNumberToUint8Clamped(Node* node) {
+  Node* const input = NodeProperties::GetValueInput(node, 0);
+  Type* const input_type = NodeProperties::GetType(input);
+  if (input_type->Is(type_cache_.kUint8)) {
+    return Replace(input);
+  }
+  return NoChange();
+}
+
 Reduction TypedOptimization::ReducePhi(Node* node) {
   // Try to narrow the type of the Phi {node}, which might be more precise now
   // after lowering based on types, i.e. a SpeculativeNumberAdd has a more