[profiler] Tracing-based CPU profiler.

src/profiler/tracing-cpu-profiler.cc

 // Copyright 2016 the V8 project 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 "src/profiler/tracing-cpu-profiler.h"
 
+#include "src/profiler/cpu-profiler.h"
+#include "src/tracing/trace-event.h"
 #include "src/v8.h"
 
+#define PROFILER_TRACE_CATEGORY_ENABLED(cat) \
+  (*TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED(TRACE_DISABLED_BY_DEFAULT(cat)))
+
 namespace v8 {
 
 std::unique_ptr<TracingCpuProfiler> TracingCpuProfiler::Create(
     v8::Isolate* isolate) {
   return std::unique_ptr<TracingCpuProfiler>(
       new internal::TracingCpuProfilerImpl(
           reinterpret_cast<internal::Isolate*>(isolate)));
 }
 
 namespace internal {
 
-TracingCpuProfilerImpl::TracingCpuProfilerImpl(Isolate* isolate) {}
+TracingCpuProfilerImpl::TracingCpuProfilerImpl(Isolate* isolate)
+    : isolate_(isolate), profiling_enabled_(false) {
+  // Make sure tracing system notices profiler categories.
+  PROFILER_TRACE_CATEGORY_ENABLED("v8.cpu_profiler");
+  PROFILER_TRACE_CATEGORY_ENABLED("v8.cpu_profiler.hires");
+  V8::GetCurrentPlatform()->AddTraceStateObserver(this);
+}
 
-TracingCpuProfilerImpl::~TracingCpuProfilerImpl() {}
+TracingCpuProfilerImpl::~TracingCpuProfilerImpl() {
+  StopProfiling();
+  V8::GetCurrentPlatform()->RemoveTraceStateObserver(this);
+}
+
+void TracingCpuProfilerImpl::OnTraceEnabled() {
+  if (!PROFILER_TRACE_CATEGORY_ENABLED("v8.cpu_profiler")) return;
+  profiling_enabled_ = true;
+  isolate_->RequestInterrupt(
+      [](v8::Isolate*, void* data) {
+        reinterpret_cast<TracingCpuProfilerImpl*>(data)->StartProfiling();
+      },
+      this);
+}
+
+void TracingCpuProfilerImpl::OnTraceDisabled() {
+  base::LockGuard<base::Mutex> lock(&mutex_);
+  if (!profiling_enabled_) return;
+  profiling_enabled_ = false;
+  isolate_->RequestInterrupt(
+      [](v8::Isolate*, void* data) {
+        reinterpret_cast<TracingCpuProfilerImpl*>(data)->StopProfiling();
+      },
+      this);
+}
+
+void TracingCpuProfilerImpl::StartProfiling() {
+  base::LockGuard<base::Mutex> lock(&mutex_);
+  if (!profiling_enabled_ || profiler_) return;
+  int sampling_interval_us =
+      PROFILER_TRACE_CATEGORY_ENABLED("v8.cpu_profiler.hires") ? 100 : 1000;
+  profiler_.reset(new CpuProfiler(isolate_));
+  profiler_->set_sampling_interval(
+      base::TimeDelta::FromMicroseconds(sampling_interval_us));
+  profiler_->StartProfiling("", true);
+}
+
+void TracingCpuProfilerImpl::StopProfiling() {
+  base::LockGuard<base::Mutex> lock(&mutex_);
+  if (!profiler_) return;
+  profiler_->StopProfiling("");
+  profiler_.reset();
+}
 
 }  // namespace internal
 }  // namespace v8