Add missing Javadoc and fix typos. (census-instrumentation#1874)

* Doc: Add a missing javadoc.

* Fix some typos.

Author: songy23

api/src/main/java/io/opencensus/metrics/MetricOptions.java

@@ -89,6 +89,11 @@ public static Builder builder() {
         .setConstantLabels(Collections.<LabelKey, LabelValue>emptyMap());
   }
 
+  /**
+   * Builder for {@link MetricOptions}.
+   *
+   * @since 0.20
+   */
   @AutoValue.Builder
   public abstract static class Builder {
 

benchmarks/src/jmh/java/io/opencensus/benchmarks/trace/SpanOperationsBenchmark.java

@@ -84,9 +84,9 @@ public static class Data {
     public void setup() {
       tracer = BenchmarksUtil.getTracer(implementation);
       attributeSpan = createSpan("Attribute");
-      annotationSpanEmpty = createSpan("AnnotaionSpanEmpty");
-      annotationSpanAttributes = createSpan("AnnotaionSpanAttributes");
-      annotationSpanAnnotation = createSpan("AnnotaionSpanAnnotation");
+      annotationSpanEmpty = createSpan("AnnotationSpanEmpty");
+      annotationSpanAttributes = createSpan("AnnotationSpanAttributes");
+      annotationSpanAnnotation = createSpan("AnnotationSpanAnnotation");
       messageEventSpan = createSpan("MessageEventSpan");
       linkSpan = createSpan("LinkSpan");
       initAttributes();