public Builder clearDescription() {
          bitField0_ = (bitField0_ & ~0x00000001);
          description_ = null;
          if (descriptionBuilder_ != null) {
            descriptionBuilder_.dispose();
            descriptionBuilder_ = null;
          }
          onChanged();
          return this;
        }
<pre>
A user-supplied message describing the event. The maximum length for
the description is 256 bytes.
</pre>

<code>.google.devtools.cloudtrace.v2.TruncatableString description = 1;</code>
java-trace/proto-google-cloud-trace-v2/src/main/java/com/google/devtools/cloudtrace/v2/Span.java