Hide empty CPU profile on class page

runtime/observatory/lib/src/elements/class_view.dart

 // Copyright (c) 2013, 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 class_view_element;
 
 import 'dart:async';
 import 'observatory_element.dart';
 import 'package:observatory/cpu_profile.dart';
 import 'package:observatory/elements.dart';
@@ skipping 44 matching lines @@
     sampleBufferControlElement =
         shadowRoot.querySelector('#sampleBufferControl');
     assert(sampleBufferControlElement != null);
     sampleBufferControlElement.onSampleBufferUpdate = onSampleBufferChange;
     sampleBufferControlElement.state =
         SampleBufferControlElement.kNotLoadedState;
     stackTraceTreeConfigElement =
         shadowRoot.querySelector('#stackTraceTreeConfig');
     assert(stackTraceTreeConfigElement != null);
     stackTraceTreeConfigElement.onTreeConfigChange = onTreeConfigChange;
+    stackTraceTreeConfigElement.show = false;
     cpuProfileTreeElement = shadowRoot.querySelector('#cpuProfileTree');
     assert(cpuProfileTreeElement != null);
     cpuProfileTreeElement.profile = sampleBufferControlElement.profile;
+    cpuProfileTreeElement.show = false;
     cls.fields.forEach((field) => field.reload());
     sampleBufferControlElement.allocationProfileClass = cls;
   }
 
   Future refresh() {
     instances = null;
     retainedBytes = null;
     mostRetained = null;
     var loads = [];
     loads.add(cls.reload());
     cls.fields.forEach((field) => loads.add(field.reload()));
     return Future.wait(loads);
   }
 
   Future refreshCoverage() {
     return cls.refreshCoverage();
   }
 
   onSampleBufferChange(CpuProfile sampleBuffer) {
+    stackTraceTreeConfigElement.show = sampleBuffer.sampleCount > 0;
+    cpuProfileTreeElement.show = sampleBuffer.sampleCount > 0;
     cpuProfileTreeElement.render();
   }
 
   onTreeConfigChange(String modeSelector, String directionSelector) {
     ProfileTreeDirection direction = ProfileTreeDirection.Exclusive;
     if (directionSelector != 'Up') {
       direction = ProfileTreeDirection.Inclusive;
     }
     ProfileTreeMode mode = ProfileTreeMode.Function;
     if (modeSelector == 'Code') {
       mode = ProfileTreeMode.Code;
     }
     cpuProfileTreeElement.direction = direction;
     cpuProfileTreeElement.mode = mode;
     cpuProfileTreeElement.render();
   }
 
   Future refreshAllocationProfile() async {
     return sampleBufferControlElement.reload(cls.isolate);
   }
 
   Future toggleAllocationTrace() {
     if (cls == null) {
       return new Future(refresh);
     }
     return cls.setTraceAllocations(!cls.traceAllocations).whenComplete(refresh);
   }
 }