tracing: Don't emit thread time on non-thread/timestamped typed events

Events on other tracks or events with explicit timestamps should not
emit a thread timestamp, as this timestamp is not reflective of their
track or timestamp.

Change-Id: I0c38488bbbb8f048151f971f68c5e4070109d14d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2233018
Commit-Queue: Eric Seckler <eseckler@chromium.org>
Auto-Submit: Eric Seckler <eseckler@chromium.org>
Reviewed-by: Stephen Nusko <nuskos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#775732}

services/tracing/public/cpp/perfetto/macros_internal.cc

@@ -29,7 +29,8 @@ base::Optional<base::trace_event::TraceEvent> CreateTraceEvent(
     const unsigned char* category_group_enabled,
     const char* name,
     unsigned int flags,
-    base::TimeTicks ts = base::TimeTicks()) {
+    base::TimeTicks ts,
+    bool explicit_track) {
   DCHECK(phase == TRACE_EVENT_PHASE_BEGIN || phase == TRACE_EVENT_PHASE_END ||
          phase == TRACE_EVENT_PHASE_INSTANT);
   DCHECK(category_group_enabled);
@@ -47,9 +48,15 @@ base::Optional<base::trace_event::TraceEvent> CreateTraceEvent(
   } else {
     flags |= TRACE_EVENT_FLAG_EXPLICIT_TIMESTAMP;
   }
-  base::ThreadTicks thread_now = ThreadNow();
-  base::trace_event::ThreadInstructionCount thread_instruction_now =
-      ThreadInstructionNow();
+
+  // Only emit thread time / instruction count for events on the default track
+  // without explicit timestamp.
+  base::ThreadTicks thread_now;
+  base::trace_event::ThreadInstructionCount thread_instruction_now;
+  if ((flags & TRACE_EVENT_FLAG_EXPLICIT_TIMESTAMP) == 0 && !explicit_track) {
+    thread_now = ThreadNow();
+    thread_instruction_now = ThreadInstructionNow();
+  }
 
   return base::trace_event::TraceEvent(
       thread_id, ts, thread_now, thread_instruction_now, phase,

services/tracing/public/cpp/perfetto/macros_internal.h

@@ -41,7 +41,8 @@ base::Optional<base::trace_event::TraceEvent> COMPONENT_EXPORT(TRACING_CPP)
                      const unsigned char* category_group_enabled,
                      const char* name,
                      unsigned int flags,
-                     base::TimeTicks timestamp);
+                     base::TimeTicks timestamp,
+                     bool explicit_track);
 
 template <
     typename TrackEventArgumentFunction = void (*)(perfetto::EventContext),
@@ -57,7 +58,8 @@ static inline base::trace_event::TraceEventHandle AddTraceEvent(
     TrackEventArgumentFunction argument_func) {
   base::trace_event::TraceEventHandle handle = {0, 0, 0};
   auto maybe_event =
-      CreateTraceEvent(phase, category_group_enabled, name, flags, timestamp);
+      CreateTraceEvent(phase, category_group_enabled, name, flags, timestamp,
+                       track.uuid != perfetto::Track().uuid);
   if (!maybe_event) {
     return handle;
   }

services/tracing/public/cpp/perfetto/trace_event_data_source_unittest.cc

@@ -539,9 +539,10 @@ class TraceEventDataSourceTest : public testing::Test {
     } else {
       EXPECT_EQ(packet->track_event().extra_counter_track_uuids_size(), 0);
       if (packet->track_event().extra_counter_values_size()) {
-        // If the event is for a different thread, then we shouldn't have thread
-        // timestamps except for the explicit thread timestamps above.
+        // If the event is for a different thread or track, we shouldn't have
+        // thread timestamps except for the explicit thread timestamps above.
         EXPECT_TRUE(tid_override == 0);
+        EXPECT_EQ(track.uuid, 0u);
         int64_t thread_time_delta =
             packet->track_event().extra_counter_values()[0];
         EXPECT_LE(last_thread_time_ + thread_time_delta,