private void ensureAllKmsKeysIsMutable() {
      if (!allKmsKeys_.isModifiable()) {
        allKmsKeys_ = new com.google.protobuf.LazyStringArrayList(allKmsKeys_);
      }
      bitField0_ |= 0x00008000;
    }
<pre>
Optional. Describes the execution history level to apply to this workflow.
</pre>

<code>
.google.cloud.workflows.v1.ExecutionHistoryLevel execution_history_level = 15 [(.google.api.field_behavior) = OPTIONAL];
</code>

@return This builder for chaining.
java-workflows/proto-google-cloud-workflows-v1/src/main/java/com/google/cloud/workflows/v1/Workflow.java