dart2js cps: Make Identical a built-in and add Interceptor to Tree IR.

pkg/compiler/lib/src/tree_ir/optimization/statement_rewriter.dart

Index: pkg/compiler/lib/src/tree_ir/optimization/statement_rewriter.dart
diff --git a/pkg/compiler/lib/src/tree_ir/optimization/statement_rewriter.dart b/pkg/compiler/lib/src/tree_ir/optimization/statement_rewriter.dart
index 4c2ad52f8e9d85f21e3ca44d01a08d9418af7d9e..68b84593ebdbc9b236477d96851e83fd25ef4a24 100644
--- a/pkg/compiler/lib/src/tree_ir/optimization/statement_rewriter.dart
+++ b/pkg/compiler/lib/src/tree_ir/optimization/statement_rewriter.dart
@@ -288,6 +288,7 @@ class StatementRewriter extends Transformer implements Pass {
            exp is This ||
            exp is CreateInvocationMirror ||
            exp is InvokeStatic && exp.isEffectivelyConstant ||
+           exp is Interceptor ||
            exp is ApplyBuiltinOperator ||
            exp is VariableUse && constantEnvironment.containsKey(exp.variable);
   }
@@ -630,6 +631,11 @@ class StatementRewriter extends Transformer implements Pass {
     return node;
   }
 
+  Expression visitInterceptor(Interceptor node) {
+    node.input = visitExpression(node.input);
+    return node;
+  }
+
   /// True if [operator] is a binary operator that always has the same value
   /// if its arguments are swapped.
   bool isSymmetricOperator(BuiltinOperator operator) {