Move all flags to CompilerOptions (first step to stop passing the compiler to

pkg/compiler/lib/src/js_emitter/program_builder/field_visitor.dart

 // Copyright (c) 2015, 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.js_emitter.program_builder;
 
 /**
  * [member] is a field (instance, static, or top level).
  *
  * [name] is the field name that the [Namer] has picked for this field's
@@ skipping 81 matching lines @@
         needsGetter = fieldNeedsGetter(field);
         needsSetter = fieldNeedsSetter(field);
       }
 
       if ((isInstantiated && !backend.isNative(holder))
           || needsGetter
           || needsSetter) {
         js.Name accessorName = namer.fieldAccessorName(field);
         js.Name fieldName = namer.fieldPropertyName(field);
         bool needsCheckedSetter = false;
-        if (compiler.enableTypeAssertions
+        if (compiler.options.enableTypeAssertions
             && needsSetter
             && !canAvoidGeneratedCheckedSetter(field)) {
           needsCheckedSetter = true;
           needsSetter = false;
         }
         // Getters and setters with suffixes will be generated dynamically.
         f(field, fieldName, accessorName, needsGetter, needsSetter,
             needsCheckedSetter);
       }
     }
@@ skipping 48 matching lines @@
       field is ClosureFieldElement;
   }
 
   bool canAvoidGeneratedCheckedSetter(VariableElement member) {
     // We never generate accessors for top-level/static fields.
     if (!member.isInstanceMember) return true;
     DartType type = member.type;
     return type.treatAsDynamic || type.isObject;
   }
 }