Expose allocation tracing over service protocol

runtime/observatory/lib/src/cpu_profile/cpu_profile.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 cpu_profiler;
 
 class CodeCallTreeNode {
   final ProfileCode profileCode;
   final int count;
   double get percentage => _percentage;
@@ skipping 580 matching lines @@
   _recordCallee(ProfileFunction callee, int count) {
     var r = callees[callee];
     if (r == null) {
       r = 0;
     }
     callees[callee] = r + count;
   }
 }
 
 
+// TODO(johnmccutchan): Rename to SampleProfile
 class CpuProfile {
   final double MICROSECONDS_PER_SECOND = 1000000.0;
   final double displayThreshold = 0.0002; // 0.02%.
 
   Isolate isolate;
 
   int sampleCount = 0;
   int samplePeriod = 0;
   double sampleRate = 0.0;
 
@@ skipping 266 matching lines @@
   int approximateMillisecondsForCount(count) {
     var MICROSECONDS_PER_MILLISECOND = 1000.0;
     return (count * samplePeriod) ~/ MICROSECONDS_PER_MILLISECOND;
   }
 
   double approximateSecondsForCount(count) {
     var MICROSECONDS_PER_SECOND = 1000000.0;
     return (count * samplePeriod) / MICROSECONDS_PER_SECOND;
   }
 }