src: fix building --without-v8-plartform

* declare v8_platform.platform_ unconditionally

  v8_platform.platform_ is referenced by node::Start
  without regard to the value of NODE_USE_V8_PLATFORM,
  so it should be declared unconditionally, otherwise
  Node fails to compile when !NODE_USE_V8_PLATFORM.

* update v8_platform.StartInspector signature

  The call signature of v8_platform.StartInspector needs
  to be the same whether or not NODE_USE_V8_PLATFORM,
  otherwise Node will fail to compile if HAVE_INSPECTOR
  and !NODE_USE_V8_PLATFORM.

* don't call tracing_agent->Start w/nullptr

  node::tracing::Agent::Start can't accept a nullptr
  argument to its platform parameter, so don't call it
  when Node is compiled with NODE_USE_V8_PLATFORM=0.

* refactor tracing_agent into v8_platform

  Move tracing_agent global into the v8_platform struct,
  renaming it to tracing_agent_; CHECK(tracing_agent_ ==
  nullptr) in StartTracingAgent() to detect double calls;
  and relace another tracing_agent->Stop() call with a call
  to StopTracingAgent().

PR-URL: #11088
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>

src/node.cc

@@ -200,7 +200,6 @@ static uv_async_t dispatch_debug_messages_async;
 
 static Mutex node_isolate_mutex;
 static v8::Isolate* node_isolate;
-static tracing::Agent* tracing_agent;
 
 static node::DebugOptions debug_options;
 
@@ -228,16 +227,33 @@ static struct {
   }
 #endif  // HAVE_INSPECTOR
 
+  void StartTracingAgent() {
+    CHECK(tracing_agent_ == nullptr);
+    tracing_agent_ = new tracing::Agent();
+    tracing_agent_->Start(platform_, trace_enabled_categories);
+  }
+
+  void StopTracingAgent() {
+    tracing_agent_->Stop();
+  }
+
   v8::Platform* platform_;
+  tracing::Agent* tracing_agent_;
 #else  // !NODE_USE_V8_PLATFORM
   void Initialize(int thread_pool_size) {}
   void PumpMessageLoop(Isolate* isolate) {}
   void Dispose() {}
   bool StartInspector(Environment *env, const char* script_path,
-                      int port, bool wait) {
+                      const node::DebugOptions& options) {
     env->ThrowError("Node compiled with NODE_USE_V8_PLATFORM=0");
     return false;  // make compiler happy
   }
+
+  void StartTracingAgent() {
+    fprintf(stderr, "Node compiled with NODE_USE_V8_PLATFORM=0, "
+                    "so event tracing is not available.\n");
+  }
+  void StopTracingAgent() {}
 #endif  // !NODE_USE_V8_PLATFORM
 } v8_platform;
 
@@ -3386,7 +3402,7 @@ void SetupProcessObject(Environment* env,
 void SignalExit(int signo) {
   uv_tty_reset_mode();
   if (trace_enabled) {
-    tracing_agent->Stop();
+    v8_platform.StopTracingAgent();
   }
 #ifdef __FreeBSD__
   // FreeBSD has a nasty bug, see RegisterSignalHandler for details
@@ -4533,15 +4549,14 @@ int Start(int argc, char** argv) {
   if (trace_enabled) {
     fprintf(stderr, "Warning: Trace event is an experimental feature "
             "and could change at any time.\n");
-    tracing_agent = new tracing::Agent();
-    tracing_agent->Start(v8_platform.platform_, trace_enabled_categories);
+    v8_platform.StartTracingAgent();
   }
   V8::Initialize();
   v8_initialized = true;
   const int exit_code =
       Start(uv_default_loop(), argc, argv, exec_argc, exec_argv);
   if (trace_enabled) {
-    tracing_agent->Stop();
+    v8_platform.StopTracingAgent();
   }
   v8_initialized = false;
   V8::Dispose();