Make stack sampling profiler sample beyond startup.

components/metrics/call_stack_profile_params.h

Index: components/metrics/call_stack_profile_params.h
diff --git a/components/metrics/call_stack_profile_params.h b/components/metrics/call_stack_profile_params.h
index 4dd7cd4fef2fecf6cb1dc02f423adc4722f092ec..0782697eca89b76e71a64c71e2672b3c74717f73 100644
--- a/components/metrics/call_stack_profile_params.h
+++ b/components/metrics/call_stack_profile_params.h
@@ -5,6 +5,8 @@
 #ifndef COMPONENTS_METRICS_CALL_STACK_PROFILE_PARAMS_H_
 #define COMPONENTS_METRICS_CALL_STACK_PROFILE_PARAMS_H_
 
+#include "base/time/time.h"
+
 namespace metrics {
 
 // Parameters to pass back to the metrics provider.
@@ -49,7 +51,8 @@ struct CallStackProfileParams {
     PROCESS_STARTUP,
     JANKY_TASK,
     THREAD_HUNG,
-    TRIGGER_LAST = THREAD_HUNG
+    PERIODIC_COLLECTION,
+    TRIGGER_LAST = PERIODIC_COLLECTION
   };
 
   // Allows the caller to specify whether sample ordering is
@@ -80,6 +83,12 @@ struct CallStackProfileParams {
 
   // Whether to preserve sample ordering.
   SampleOrderingSpec ordering_spec;
+
+  // The time at which the CallStackProfileMetricsProvider became aware of the
+  // request for profiling. In particular, this is when callback was requested
+  // via CallStackProfileMetricsProvider::GetProfilerCallback(). Used to
+  // determine if collection was disabled during the collection of the profile.
+  base::TimeTicks start_timestamp;
 };
 
 }  // namespace metrics