Add TraceOptions (open-telemetry#60)

* TraceOptions

* export TRACE_OPTIONS_SAMPLED and TRACE_OPTIONS_UNSAMPLED

* Fix review comments

* Rename TRACE_OPTIONS_SAMPLED -> SAMPLED

* Add SampleOptions enum

* Add TraceOptions as enum

Author: mayurkale22

packages/opentelemetry-types/src/trace/span_context.ts

@@ -39,8 +39,11 @@ export interface SpanContext {
    * Trace options to propagate.
    *
    * It is represented as 1 byte (bitmap). Bit to represent whether trace is
-   * sampled or not.
-   * SAMPLED_VALUE = 0x1 and NOT_SAMPLED_VALUE = 0x0;
+   * sampled or not. When set, the least significant bit documents that the
+   * caller may have recorded trace data. A caller who does not record trace
+   * data out-of-band leaves this flag unset.
+   *
+   * SAMPLED = 0x1 and UNSAMPLED = 0x0;
    */
   traceOptions?: TraceOptions;
   /**

packages/opentelemetry-types/src/trace/trace_options.ts

@@ -14,6 +14,9 @@
  * limitations under the License.
  */
 
-export interface TraceOptions {
-  // TODO
+export enum TraceOptions {
+  /** Bit to represent whether trace is unsampled in trace options. */
+  UNSAMPLED = 0x0,
+  /** Bit to represent whether trace is sampled in trace options. */
+  SAMPLED = 0x1,
 }