Document SonarStep.h

Summary: It may not be immediately obvious how this works, so adding comments.

Reviewed By: passy

Differential Revision: D9333321

fbshipit-source-id: 79740b3d2a9589b3ba48c47b0068afdaf26f35a3

xplat/Sonar/SonarStep.h

@@ -14,8 +14,14 @@ class SonarState;
 
 class SonarStep {
  public:
+  /* Mark this step as completed successfully
+   * failing to call complete() will be registered as a failure
+   * when the destructor is executed. */
   void complete();
+
+  // Mark the step as failed, and provide a message.
   void fail(std::string message);
+
   SonarStep(std::string name, SonarState* state);
   ~SonarStep();