Hide empty CPU profile on class page

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

Index: runtime/observatory/lib/src/elements/class_view.dart
diff --git a/runtime/observatory/lib/src/elements/class_view.dart b/runtime/observatory/lib/src/elements/class_view.dart
index cfd535b1a2b47e8a057c6da34e7329a77790d7ef..998f82d6a914ab1fed3f502c79ccfc4524abfcf9 100644
--- a/runtime/observatory/lib/src/elements/class_view.dart
+++ b/runtime/observatory/lib/src/elements/class_view.dart
@@ -62,9 +62,11 @@ class ClassViewElement extends ObservatoryElement {
         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;
   }
@@ -84,6 +86,8 @@ class ClassViewElement extends ObservatoryElement {
   }
 
   onSampleBufferChange(CpuProfile sampleBuffer) {
+    stackTraceTreeConfigElement.show = sampleBuffer.sampleCount > 0;
+    cpuProfileTreeElement.show = sampleBuffer.sampleCount > 0;
     cpuProfileTreeElement.render();
   }