Be smarter about when to disable global type inference.

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

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart2js;
 
 /**
  * If true, print a warning for each method that was resolved, but not
  * compiled.
  */
@@ skipping 435 matching lines @@
   static const int PHASE_SCANNING = 0;
   static const int PHASE_RESOLVING = 1;
   static const int PHASE_DONE_RESOLVING = 2;
   static const int PHASE_COMPILING = 3;
   int phase;
 
   bool compilationFailed = false;
 
   bool hasCrashed = false;
 
+  /// Set by the backend if real reflection is detected in use of dart:mirrors.
+  bool disableTypeInferenceForMirrors = false;
+
   Compiler({this.tracer: const Tracer(),
             this.enableTypeAssertions: false,
             this.enableUserAssertions: false,
             this.trustTypeAnnotations: false,
             this.enableConcreteTypeInference: false,
             this.disableTypeInferenceFlag: false,
             this.maxConcreteTypeSize: 5,
             this.enableMinification: false,
             this.enableNativeLiveTypeAnalysis: false,
             bool emitJavaScript: true,
@@ skipping 57 matching lines @@
   Universe get codegenWorld => enqueuer.codegen.universe;
 
   bool get hasBuildId => buildId != UNDETERMINED_BUILD_ID;
 
   bool get mirrorsEnabled => mirrorSystemClass != null;
 
   bool get analyzeAll => analyzeAllFlag || compileAll;
 
   bool get compileAll => false;
 
-  bool get disableTypeInference => disableTypeInferenceFlag || mirrorsEnabled;
+  bool get disableTypeInference {
+    return disableTypeInferenceFlag || disableTypeInferenceForMirrors;
+  }
 
   int getNextFreeClassId() => nextFreeClassId++;
 
   void ensure(bool condition) {
     if (!condition) cancel('failed assertion in leg');
   }
 
   void unimplemented(String methodName,
                      {Node node, Token token, HInstruction instruction,
                       Element element}) {
@@ skipping 848 matching lines @@
 
   void close() {}
 
   toString() => name;
 
   /// Convenience method for getting an [api.CompilerOutputProvider].
   static NullSink outputProvider(String name, String extension) {
     return new NullSink('$name.$extension');
   }
 }