Tracing: Add more DCHECKS to get more info on recent test flakiness

base/trace_event/trace_log.cc

 // Copyright 2015 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 "base/trace_event/trace_log.h"
 
 #include <algorithm>
 #include <cmath>
 #include <memory>
 #include <utility>
@@ skipping 156 matching lines @@
 
 // Use this function instead of TraceEventHandle constructor to keep the
 // overhead of ScopedTracer (trace_event.h) constructor minimum.
 void MakeHandle(uint32_t chunk_seq,
                 size_t chunk_index,
                 size_t event_index,
                 TraceEventHandle* handle) {
   DCHECK(chunk_seq);
   DCHECK(chunk_index <= TraceBufferChunk::kMaxChunkIndex);
   DCHECK(event_index < TraceBufferChunk::kTraceBufferChunkSize);
+  DCHECK(chunk_index <= std::numeric_limits<uint16_t>::max());
   handle->chunk_seq = chunk_seq;
   handle->chunk_index = static_cast<uint16_t>(chunk_index);
   handle->event_index = static_cast<uint16_t>(event_index);
 }
 
 }  // namespace
 
 // A helper class that allows the lock to be acquired in the middle of the scope
 // and unlocks at the end of scope if locked.
 class TraceLog::OptionalAutoLock {
@@ skipping 1414 matching lines @@
 
 TraceEvent* TraceLog::GetEventByHandle(TraceEventHandle handle) {
   return GetEventByHandleInternal(handle, NULL);
 }
 
 TraceEvent* TraceLog::GetEventByHandleInternal(TraceEventHandle handle,
                                                OptionalAutoLock* lock) {
   if (!handle.chunk_seq)
     return NULL;
 
+  DCHECK(handle.chunk_seq);
+  DCHECK(handle.chunk_index <= TraceBufferChunk::kMaxChunkIndex);
+  DCHECK(handle.event_index < TraceBufferChunk::kTraceBufferChunkSize);
+
   if (thread_local_event_buffer_.Get()) {
     TraceEvent* trace_event =
         thread_local_event_buffer_.Get()->GetEventByHandle(handle);
     if (trace_event)
       return trace_event;
   }
 
   // The event has been out-of-control of the thread local buffer.
   // Try to get the event from the main buffer with a lock.
   if (lock)
@@ skipping 158 matching lines @@
 }
 
 ScopedTraceBinaryEfficient::~ScopedTraceBinaryEfficient() {
   if (*category_group_enabled_) {
     TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION(category_group_enabled_, name_,
                                                 event_handle_);
   }
 }
 
 }  // namespace trace_event_internal