Support duration events in `benchmark.mojo`.

apps/benchmark/measurements.h

Index: apps/benchmark/measurements.h
diff --git a/apps/benchmark/measurements.h b/apps/benchmark/measurements.h
index eeb472795e39236664c41acc56a5d7e643184339..a89665ed742b3b2ad0d2cce2f960e60da898d94b 100644
--- a/apps/benchmark/measurements.h
+++ b/apps/benchmark/measurements.h
@@ -18,10 +18,10 @@ namespace benchmark {
 // Describes a trace event to match.
 struct EventSpec {
   std::string name;
-  std::string category;
+  std::string categories;
 
   EventSpec();
-  EventSpec(std::string name, std::string category);
+  EventSpec(std::string name, std::string categories);
   ~EventSpec();
 };
 
@@ -38,7 +38,7 @@ struct Measurement {
   Measurement();
   Measurement(MeasurementType type,
               std::string target_name,
-              std::string target_category);
+              std::string target_categories);
   ~Measurement();
 };