Fix occasional failure in compaction_job_test

Summary: Coverage test has been occasionally failing due to this timing check.

Test Plan: run test

Reviewers: yhchiang

Reviewed By: yhchiang

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D41367

db/compaction_job_test.cc

@@ -168,9 +168,8 @@ void VerifyInitializationOfCompactionJobStats(
 void VerifyCompactionJobStats(
     const CompactionJobStats& compaction_job_stats,
     const std::vector<FileMetaData*>& files,
-    size_t num_output_files,
-    uint64_t min_elapsed_time) {
-  ASSERT_GE(compaction_job_stats.elapsed_micros, min_elapsed_time);
+    size_t num_output_files) {
+  ASSERT_GE(compaction_job_stats.elapsed_micros, 0U);
   ASSERT_EQ(compaction_job_stats.num_input_files, files.size());
   ASSERT_EQ(compaction_job_stats.num_output_files, num_output_files);
 }
@@ -209,7 +208,6 @@ TEST_F(CompactionJobTest, Simple) {
                                std::move(yield_callback), &event_logger, false,
                                db_name, &compaction_job_stats);
 
-  auto start_micros = Env::Default()->NowMicros();
   VerifyInitializationOfCompactionJobStats(compaction_job_stats);
 
   compaction_job.Prepare();
@@ -223,7 +221,7 @@ TEST_F(CompactionJobTest, Simple) {
 
   VerifyCompactionJobStats(
       compaction_job_stats,
-      files, 1, (Env::Default()->NowMicros() - start_micros) / 2);
+      files, 1);
 
   mock_table_factory_->AssertLatestFile(expected_results);
   ASSERT_EQ(yield_callback_called, 20000);