Add 'Math' to list of safe global JavaScript names.

pkg/compiler/lib/src/js/placeholder_safety.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.
 
 
 library js.safety;
 
 import "js.dart" as js;
 
 typedef bool PositionPredicate(int position);
@@ skipping 285 matching lines @@
 
   int visitVariableUse(js.VariableUse node) {
     // We could get a ReferenceError unless the variable is in scope.  For JS
     // fragments, the only use of VariableUse outside a `function(){...}` should
     // be for global references. Certain global names are almost certainly not
     // reference errors, e.g 'Array'.
     switch (node.name) {
       case 'Array':
       case 'Date':
       case 'Function':
+      case 'Math':
       case 'Number':
       case 'Object':
       case 'RegExp':
       case 'String':
       case 'self':
       case 'window':
         return NONNULL_VALUE;
       default:
         return unsafe(UNKNOWN_VALUE);
     }
   }
 
   int visitFun(js.Fun node) {
     bool oldSafe = safe;
     int oldNextPosition = nextPosition;
     visit(node.body);
     // Creating a function has no effect on order unless there are embedded
     // placeholders.
     safe = (nextPosition == oldNextPosition) && oldSafe;
     return NONNULL_VALUE;
   }
 }