Rename TraceEvent namepsace to trace_event

https://google.github.io/styleguide/cppguide.html#Namespace_Names
> Namespace names are all lower-case.

This CL has no behavior changes.

Bug: 889726
Change-Id: I0dbad4a299ae4ce3be3696da7703822d87d151d5
Reviewed-on: https://chromium-review.googlesource.com/c/1325288Reviewed-by: Kent Tamura <tkent@chromium.org>
Commit-Queue: Zhuoyu Qian <zhuoyu.qian@samsung.com>
Cr-Commit-Position: refs/heads/master@{#606682}

third_party/blink/renderer/core/inspector/inspector_trace_events.cc

@@ -212,7 +212,7 @@ void InspectorTraceEvents::PaintTiming(Document* document,
                                        const char* name,
                                        double timestamp) {
   TRACE_EVENT_MARK_WITH_TIMESTAMP2("loading,rail,devtools.timeline", name,
-                                   TraceEvent::ToTraceTimestamp(timestamp),
+                                   trace_event::ToTraceTimestamp(timestamp),
                                    "frame", ToTraceValue(document->GetFrame()),
                                    "data", GetNavigationTracingData(document));
 }

third_party/blink/renderer/core/inspector/worker_inspector_controller.cc

@@ -93,13 +93,13 @@ WorkerInspectorController::WorkerInspectorController(
                         std::move(devtools_params->agent_request),
                         thread->GetTaskRunner(TaskType::kInternalInspector));
   }
-  TraceEvent::AddEnabledStateObserver(this);
+  trace_event::AddEnabledStateObserver(this);
   EmitTraceEvent();
 }
 
 WorkerInspectorController::~WorkerInspectorController() {
   DCHECK(!thread_);
-  TraceEvent::RemoveEnabledStateObserver(this);
+  trace_event::RemoveEnabledStateObserver(this);
 }
 
 void WorkerInspectorController::AttachSession(DevToolsSession* session,

third_party/blink/renderer/core/inspector/worker_inspector_controller.h

@@ -54,7 +54,7 @@ struct WorkerDevToolsParams;
 
 class WorkerInspectorController final
     : public GarbageCollectedFinalized<WorkerInspectorController>,
-      public TraceEvent::EnabledStateObserver,
+      public trace_event::EnabledStateObserver,
       public DevToolsAgent::Client,
       private Thread::TaskObserver {
  public:
@@ -81,7 +81,7 @@ class WorkerInspectorController final
   void WillProcessTask(const base::PendingTask&) override;
   void DidProcessTask(const base::PendingTask&) override;
 
-  // blink::TraceEvent::EnabledStateObserver implementation:
+  // blink::trace_event::EnabledStateObserver implementation:
   void OnTraceLogEnabled() override;
   void OnTraceLogDisabled() override;
 

third_party/blink/renderer/core/timing/performance_user_timing.cc

@@ -201,11 +201,11 @@ PerformanceMeasure* UserTiming::Measure(ScriptState* script_state,
   TRACE_EVENT_COPY_NESTABLE_ASYNC_BEGIN_WITH_TIMESTAMP0(
       "blink.user_timing", measure_name.Utf8().data(),
       WTF::StringHash::GetHash(measure_name),
-      TraceEvent::ToTraceTimestamp(start_time_monotonic));
+      trace_event::ToTraceTimestamp(start_time_monotonic));
   TRACE_EVENT_COPY_NESTABLE_ASYNC_END_WITH_TIMESTAMP0(
       "blink.user_timing", measure_name.Utf8().data(),
       WTF::StringHash::GetHash(measure_name),
-      TraceEvent::ToTraceTimestamp(end_time_monotonic));
+      trace_event::ToTraceTimestamp(end_time_monotonic));
 
   PerformanceMeasure* measure = PerformanceMeasure::Create(
       script_state, measure_name, start_time, end_time, detail);

third_party/blink/renderer/platform/instrumentation/tracing/trace_event.cc

@@ -7,7 +7,7 @@
 #include "base/trace_event/trace_event.h"
 
 namespace blink {
-namespace TraceEvent {
+namespace trace_event {
 
 void EnableTracing(const String& category_filter) {
   base::trace_event::TraceLog::GetInstance()->SetEnabled(
@@ -39,5 +39,5 @@ void RemoveEnabledStateObserver(EnabledStateObserver* observer) {
       observer);
 }
 
-}  // namespace TraceEvent
+}  // namespace trace_event
 }  // namespace blink

third_party/blink/renderer/platform/instrumentation/tracing/trace_event.h

@@ -26,7 +26,7 @@ static inline void SetTraceValue(const CString& arg,
 }  // namespace WTF
 
 namespace blink {
-namespace TraceEvent {
+namespace trace_event {
 
 using base::trace_event::TraceScopedTrackableObject;
 using AsyncEnabledStateObserver =
@@ -51,7 +51,7 @@ PLATFORM_EXPORT void RemoveAsyncEnabledStateObserver(
 PLATFORM_EXPORT void AddEnabledStateObserver(EnabledStateObserver*);
 PLATFORM_EXPORT void RemoveEnabledStateObserver(EnabledStateObserver*);
 
-}  // namespace TraceEvent
+}  // namespace trace_event
 }  // namespace blink
 
 #endif

third_party/blink/tools/blinkpy/presubmit/audit_non_blink_usage.py

@@ -241,6 +241,7 @@ _CONFIG = [
             'style_change_extra_data::.+',
             'style_change_reason::.+',
             'svg_path_parser::.+',
+            'trace_event::.+',
             'touch_action_util::.+',
             'vector_math::.+',
             'web_core_test_support::.+',