LatencyInfo trace_id_ no longer dependent on sequence_number.

ui/latency/latency_info.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/latency/latency_info.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <string>
@@ skipping 117 matching lines @@
 
 }  // namespace
 
 namespace ui {
 
 LatencyInfo::LatencyInfo() : LatencyInfo(SourceEventType::UNKNOWN) {}
 
 LatencyInfo::LatencyInfo(SourceEventType type)
     : trace_id_(-1),
       coalesced_(false),
+      began_(false),
       terminated_(false),
       source_event_type_(type) {}
 
 LatencyInfo::LatencyInfo(const LatencyInfo& other) = default;
 
 LatencyInfo::~LatencyInfo() {}
 
 LatencyInfo::LatencyInfo(int64_t trace_id, bool terminated)
     : trace_id_(trace_id),
+      began_(false),
       terminated_(terminated),
       source_event_type_(SourceEventType::UNKNOWN) {}
 
 bool LatencyInfo::Verify(const std::vector<LatencyInfo>& latency_info,
                          const char* referring_msg) {
   if (latency_info.size() > kMaxLatencyInfoNumber) {
     LOG(ERROR) << referring_msg << ", LatencyInfo vector size "
                << latency_info.size() << " is too big.";
     TRACE_EVENT_INSTANT1("input,benchmark", "LatencyInfo::Verify Fails",
                          TRACE_EVENT_SCOPE_GLOBAL,
                          "size", latency_info.size());
     return false;
   }
   return true;
 }
 
 void LatencyInfo::CopyLatencyFrom(const LatencyInfo& other,
                                   LatencyComponentType type) {
   for (const auto& lc : other.latency_components()) {
     if (lc.first.first == type) {
       AddLatencyNumberWithTimestamp(lc.first.first,
                                     lc.first.second,
                                     lc.second.sequence_number,
                                     lc.second.event_time,
                                     lc.second.event_count);
     }
   }
+  trace_id_ = other.trace_id();
+  coalesced_ = other.coalesced();
+  // TODO(tdresser): Ideally we'd copy |began_| here as well, but |began_| isn't
+  // very intuitive, and we can actually begin multiple times across copied
+  // events.
+  terminated_ = other.terminated();
 }
 
 void LatencyInfo::AddNewLatencyFrom(const LatencyInfo& other) {
   for (const auto& lc : other.latency_components()) {
     if (!FindLatency(lc.first.first, lc.first.second, NULL)) {
       AddLatencyNumberWithTimestamp(lc.first.first,
                                     lc.first.second,
                                     lc.second.sequence_number,
                                     lc.second.event_time,
                                     lc.second.event_count);
     }
   }
+  trace_id_ = other.trace_id();
+  coalesced_ = other.coalesced();
+  // TODO(tdresser): Ideally we'd copy |began_| here as well, but |began_| isn't
+  // very intuitive, and we can actually begin multiple times across copied
+  // events.
+  terminated_ = other.terminated();
 }
 
 void LatencyInfo::AddLatencyNumber(LatencyComponentType component,
                                    int64_t id,
                                    int64_t component_sequence_number) {
   AddLatencyNumberWithTimestampImpl(component, id, component_sequence_number,
                                     base::TimeTicks::Now(), 1, nullptr);
 }
 
 void LatencyInfo::AddLatencyNumberWithTraceName(
@@ skipping 20 matching lines @@
     int64_t id,
     int64_t component_sequence_number,
     base::TimeTicks time,
     uint32_t event_count,
     const char* trace_name_str) {
   const unsigned char* latency_info_enabled =
       g_latency_info_enabled.Get().latency_info_enabled;
 
   if (IsBeginComponent(component)) {
     // Should only ever add begin component once.
-    CHECK_EQ(-1, trace_id_);
-    trace_id_ = component_sequence_number;
+    CHECK(!began_);
+    began_ = true;
+    // We should have a trace ID assigned by now.
+    DCHECK(trace_id_ != -1);
 
     if (*latency_info_enabled) {
       // The timestamp for ASYNC_BEGIN trace event is used for drawing the
       // beginning of the trace event in trace viewer. For better visualization,
       // for an input event, we want to draw the beginning as when the event is
       // originally created, e.g. the timestamp of its ORIGINAL/UI_COMPONENT,
       // not when we actually issue the ASYNC_BEGIN trace event.
       LatencyComponent begin_component;
       base::TimeTicks ts;
       if (FindLatency(INPUT_EVENT_LATENCY_ORIGINAL_COMPONENT,
@@ skipping 42 matching lines @@
       // Do a weighted average, so that the new event_time is the average of
       // the times of events currently in this structure with the time passed
       // into this method.
       it->second.event_time += (time - it->second.event_time) * event_count /
           new_count;
       it->second.event_count = new_count;
       it->second.last_event_time = std::max(it->second.last_event_time, time);
     }
   }
 
-  if (IsTerminalComponent(component) && trace_id_ != -1) {
+  if (IsTerminalComponent(component) && began_) {
     // Should only ever add terminal component once.
     CHECK(!terminated_);
     terminated_ = true;
 
     if (*latency_info_enabled) {
       TRACE_EVENT_COPY_ASYNC_END1(
           kTraceCategoriesForAsyncEvents, trace_name_.c_str(),
           TRACE_ID_DONT_MANGLE(trace_id_), "data", AsTraceableData());
     }
 
@@ skipping 55 matching lines @@
   LatencyMap::iterator it = latency_components_.begin();
   while (it != latency_components_.end()) {
     if (it->first.first == type)
       it = latency_components_.erase(it);
     else
       it++;
   }
 }
 
 }  // namespace ui