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;

[Mike Wittman, 2017/07/01 02:44:06]

Do we need to move this from a callback param to inside CallStackProfileParams
if we use the wrapper callback approach? I'm concerned that this makes it very
easy to miss the extra step required to set this value after construction,
whereas providing as a callback parameter is checked by the compiler.

 };
 
 }  // namespace metrics