Flags yellow for annotations that match case insensitive error

Particularly, this flags existing finagle formatted errors, like so:
"Server Send Error: TimeoutException: socket timed out"

Fixes #1472
See openzipkin/openzipkin.github.io#52

zipkin-ui/js/component_ui/spanPanel.js

@@ -2,6 +2,14 @@ import {component} from 'flightjs';
 import $ from 'jquery';
 import {Constants} from './traceConstants';
 
+// Annotation values that contain the word "error" hint of a transient error.
+// This adds a class when that's the case.
+export function maybeMarkTransientError(row, anno) {
+  if (/error/i.test(anno.value)) {
+    row.addClass('anno-error-transient');
+  }
+}
+
 // annotations are named events which shouldn't hold json. If someone passed
 // json, format as a single line. That way the rows corresponding to timestamps
 // aren't disrupted.
@@ -42,9 +50,7 @@ export default component(function spanPanel() {
     const $annoBody = this.$node.find('#annotations tbody').text('');
     $.each((span.annotations || []), (i, anno) => {
       const $row = self.$annotationTemplate.clone();
-      if (anno.value === Constants.ERROR) {
-        $row.addClass('anno-error-transient');
-      }
+      maybeMarkTransientError($row, anno);
       $row.find('td').each(function() {
         const $this = $(this);
         const unformattedValue = anno[$this.data('key')];

zipkin-ui/test/component_ui/spanPanel.test.js

@@ -1,10 +1,48 @@
+import {Constants} from '../../js/component_ui/traceConstants';
 import {
+  maybeMarkTransientError,
   formatAnnotationValue,
   formatBinaryAnnotationValue
 } from '../../js/component_ui/spanPanel';
+import {endpoint, annotation} from './traceTestHelpers';
+
+const ep = endpoint(123, 123, 'service1');
 
 chai.config.truncateThreshold = 0;
 
+describe('maybeMarkTransientError', () => {
+  const row = {
+    className: '',
+    addClass(className) {this.className = className;}
+  };
+
+  it('should not add class when annotation is not error', () => {
+    const anno = annotation(100, Constants.CLIENT_SEND, ep);
+
+    maybeMarkTransientError(row, anno);
+    row.className.should.equal('');
+  });
+
+  it('should add class when annotation is error', () => {
+    const anno = annotation(100, Constants.ERROR, ep);
+
+    maybeMarkTransientError(row, anno);
+    row.className.should.equal('anno-error-transient');
+  });
+
+  // uses an actual value from Finagle
+  it('should add class when annotation matches error', () => {
+    const anno = annotation(
+      100,
+      'Server Send Error: TimeoutException: socket timed out',
+      ep
+    );
+
+    maybeMarkTransientError(row, anno);
+    row.className.should.equal('anno-error-transient');
+  });
+});
+
 describe('formatAnnotationValue', () => {
   it('should return same value when string', () => {
     formatAnnotationValue('foo').should.equal('foo');