src: add public API for managing NodePlatform

PR-URL: #16981
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

src/node.cc

@@ -4043,6 +4043,18 @@ void FreeEnvironment(Environment* env) {
 }
 
 
+MultiIsolatePlatform* CreatePlatform(
+    int thread_pool_size,
+    v8::TracingController* tracing_controller) {
+  return new NodePlatform(thread_pool_size, tracing_controller);
+}
+
+
+void FreePlatform(MultiIsolatePlatform* platform) {
+  delete platform;
+}
+
+
 inline int Start(Isolate* isolate, IsolateData* isolate_data,
                  int argc, const char* const* argv,
                  int exec_argc, const char* const* exec_argv) {

src/node.h

@@ -97,6 +97,11 @@
 // Forward-declare libuv loop
 struct uv_loop_s;
 
+// Forward-declare TracingController, used by CreatePlatform.
+namespace v8 {
+class TracingController;
+}
+
 // Forward-declare these functions now to stop MSVS from becoming
 // terminally confused when it's done in node_internals.h
 namespace node {
@@ -243,6 +248,11 @@ NODE_EXTERN Environment* CreateEnvironment(IsolateData* isolate_data,
 NODE_EXTERN void LoadEnvironment(Environment* env);
 NODE_EXTERN void FreeEnvironment(Environment* env);
 
+NODE_EXTERN MultiIsolatePlatform* CreatePlatform(
+    int thread_pool_size,
+    v8::TracingController* tracing_controller);
+NODE_EXTERN void FreePlatform(MultiIsolatePlatform* platform);
+
 NODE_EXTERN void EmitBeforeExit(Environment* env);
 NODE_EXTERN int EmitExit(Environment* env);
 NODE_EXTERN void RunAtExit(Environment* env);