tp: record perf_sample source stops due to a guardrail as a stats entry

Simply put:
  perf_guardrail_stop[perf_session_id]: timestamp

Using perf_session_id (as already used by perf_sample and
perf_counter_track tables) as an index for the possible case of multiple
data sources in a trace.

Change-Id: I1e7c751ac666a02dcc296cc7433f091cf616b34a

src/trace_processor/importers/proto/profile_module.cc

diff --git a/src/trace_processor/importers/proto/profile_module.cc b/src/trace_processor/importers/proto/profile_module.cc
index 5f56041..ca72192 100644
--- a/src/trace_processor/importers/proto/profile_module.cc
+++ b/src/trace_processor/importers/proto/profile_module.cc
@@ -165,6 +165,11 @@
   const auto& sample_raw = decoder.perf_sample();
   PerfSample::Decoder sample(sample_raw.data, sample_raw.size);
 
+  uint32_t seq_id = decoder.trusted_packet_sequence_id();
+  PerfSampleTracker::SamplingStreamInfo sampling_stream =
+      context_->perf_sample_tracker->GetSamplingStreamInfo(
+          seq_id, sample.cpu(), sequence_state->GetTracePacketDefaults());
+
   // Not a sample, but an indication of data loss in the ring buffer shared with
   // the kernel.
   if (sample.kernel_records_lost() > 0) {
@@ -191,19 +196,23 @@
   }
 
   // Not a sample, but an event from the producer.
-  // TODO(rsavitski): parse abrupt stops, and see if we can propagate syscall
-  // failures to this field.
+  // TODO(rsavitski): this stat is indexed by the session id, but the older
+  // stats (see above) aren't. The indexing is relevant if a trace contains more
+  // than one profiling data source. So the older stats should be changed to
+  // being indexed as well.
   if (sample.has_producer_event()) {
+    PerfSample::ProducerEvent::Decoder producer_event(sample.producer_event());
+    if (producer_event.source_stop_reason() ==
+        PerfSample::ProducerEvent::PROFILER_STOP_GUARDRAIL) {
+      context_->storage->SetIndexedStats(
+          stats::perf_guardrail_stop_ts,
+          static_cast<int>(sampling_stream.perf_session_id), ts);
+    }
     return;
   }
 
   // Proper sample, populate the |perf_sample| table with everything except the
   // recorded counter values, which go to |counter|.
-  uint32_t seq_id = decoder.trusted_packet_sequence_id();
-  PerfSampleTracker::SamplingStreamInfo sampling_stream =
-      context_->perf_sample_tracker->GetSamplingStreamInfo(
-          seq_id, sample.cpu(), sequence_state->GetTracePacketDefaults());
-
   context_->event_tracker->PushCounter(
       ts, static_cast<double>(sample.timebase_count()),
       sampling_stream.timebase_track_id);

src/trace_processor/storage/stats.h

diff --git a/src/trace_processor/storage/stats.h b/src/trace_processor/storage/stats.h
index 16d6e63..28869c5 100644
--- a/src/trace_processor/storage/stats.h
+++ b/src/trace_processor/storage/stats.h
@@ -176,7 +176,8 @@
       "An ftrace packet was seen before the tracing start timestamp from "     \
       "the tracing service. This happens if the ftrace buffers were not "      \
       "cleared properly. These packets are silently dropped by trace "         \
-      "processor.")
+      "processor."),                                                           \
+  F(perf_guardrail_stop_ts,             kIndexed, kDataLoss, kTrace,    "")
 // clang-format on
 
 enum Type {