tracing: Workaround to thread names from killed processes

The trace importer can't handle thread descriptors from killed
processes. So, do not emit thread names/types in thread descriptors when
privacy filtering is enabled. Metadata from trace log is sufficient.

BUG=978093

Change-Id: Iff2b870edff1f1c516eec3068489e67a66cc5b8a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1691008Reviewed-by: Eric Seckler <eseckler@chromium.org>
Commit-Queue: ssid <ssid@chromium.org>
Cr-Commit-Position: refs/heads/master@{#676158}

base/trace_event/trace_log.cc

@@ -1562,7 +1562,8 @@ void TraceLog::AddMetadataEventsWhileLocked() {
   }
 
   // TODO(ssid): Stop emitting and tracking thread names when perfetto is
-  // enabled. The JSON exporter will emit thread names.
+  // enabled and after crbug/978093 if fixed. The JSON exporter will emit thread
+  // names from thread descriptors.
   AutoLock thread_info_lock(thread_info_lock_);
   for (const auto& it : thread_names_) {
     if (it.second.empty())

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

@@ -259,11 +259,9 @@ class TraceEventDataSourceTest : public testing::Test {
     }
     if (filtering_enabled) {
       EXPECT_FALSE(packet->thread_descriptor().has_thread_name());
-    } else {
-      EXPECT_EQ(kTestThread, packet->thread_descriptor().thread_name());
+      EXPECT_EQ(perfetto::protos::ThreadDescriptor::CHROME_THREAD_MAIN,
+                packet->thread_descriptor().chrome_thread_type());
     }
-    EXPECT_EQ(perfetto::protos::ThreadDescriptor::CHROME_THREAD_MAIN,
-              packet->thread_descriptor().chrome_thread_type());
 
     last_timestamp_ = packet->thread_descriptor().reference_timestamp_us();
     last_thread_time_ = packet->thread_descriptor().reference_thread_time_us();

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

@@ -553,10 +553,15 @@ void TrackEventThreadLocalEventSink::EmitThreadDescriptor(
     thread_name_ = maybe_new_name;
     thread_type_ = GetThreadType(maybe_new_name);
   }
-  if (!privacy_filtering_enabled_ && !thread_name_.empty()) {
-    thread_descriptor->set_thread_name(thread_name_.c_str());
+  // TODO(ssid): Adding name and type to thread descriptor adds thread names
+  // from killed processes. The catapult trace importer can't handle different
+  // processes with same process ids. To workaround this issue, we do not emit
+  // name and type when filtering is enabled (when metadata is not emitted).
+  // Thread names will be emitted by trace log at metadata generation step when
+  // filtering is not enabled. See crbug/978093.
+  if (privacy_filtering_enabled_) {
+    thread_descriptor->set_chrome_thread_type(thread_type_);
   }
-  thread_descriptor->set_chrome_thread_type(thread_type_);
 
   if (explicit_timestamp || !trace_event) {
     // Don't use a user-provided timestamp as a reference timestamp.