Move compile-time constant registrations to the backend.

sdk/lib/_internal/compiler/implementation/mirrors_used.dart

Index: sdk/lib/_internal/compiler/implementation/mirrors_used.dart
diff --git a/sdk/lib/_internal/compiler/implementation/mirrors_used.dart b/sdk/lib/_internal/compiler/implementation/mirrors_used.dart
index 98707c653cd0d4e1f7833997f182bf2c8c3fb43c..aad7d8b67b83f381ac04c413015c95d651ee4d6e 100644
--- a/sdk/lib/_internal/compiler/implementation/mirrors_used.dart
+++ b/sdk/lib/_internal/compiler/implementation/mirrors_used.dart
@@ -134,11 +134,11 @@ class MirrorUsageAnalyzerTask extends CompilerTask {
     for (Node argument in node.send.arguments) {
       NamedArgument named = argument.asNamedArgument();
       if (named == null) continue;
-      Constant value = compiler.metadataHandler.compileNodeWithDefinitions(
+      Constant value = compiler.constantHandler.compileNodeWithDefinitions(
           named.expression, mapping, isConst: true);
 
       ConstantMapper mapper =
-          new ConstantMapper(compiler.metadataHandler, mapping, compiler);
+          new ConstantMapper(compiler.constantHandler, mapping, compiler);
       named.expression.accept(mapper);
 
       MirrorUsageBuilder builder =