Switch how we track whether trackDdcProfile is set to reduce the performance impact. sra was seeing…

tool/input_sdk/private/ddc_runtime/operations.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.
 
 /// This library defines runtime operations on objects used by the code
 /// generator.
 part of dart._runtime;
 
 _canonicalFieldName(obj, name, args, displayName) => JS('', '''(() => {
   $name = $canonicalMember($obj, $name);
@@ skipping 164 matching lines @@
     ret.add([key, count]);
   }
 
   return ret;
 }
 
 clearDynamicStats() {
   _callMethodStats.clear();
 }
 
+bool trackProfile = JS('bool', 'dart.global.trackDdcProfile');
+
 _trackCall(obj, name) {
-  if (JS('bool', '!dart.global.trackDdcProfile')) return;
+  if (JS('bool', '!#', trackProfile)) return;
+
   var actual = getReifiedType(obj);
   String stackStr = JS('String', "new Error().stack");
   var stack = stackStr.split('\n    at ');
   var src = '';
   for (int i = 2; i < stack.length; ++i) {
     var frame = stack[i];
     if (!frame.contains('dev_compiler/lib/runtime/dart_sdk.js')) {
       src = frame;
       break;
     }
@@ skipping 449 matching lines @@
     constructor(dartIterator) {
       this.dartIterator = dartIterator;
     }
     next() {
       let i = this.dartIterator;
       let done = !i.moveNext();
       return { done: done, value: done ? void 0 : i.current };
     }
   }
 ''');