src: drop homegrown thread pool, use libplatform

Drop the homegrown thread pool that was introduced in commit 50839a0
("v8_platform: provide default v8::Platform impl") and use one from
V8's libplatform library.  Performance is comparable and it removes
a few hundred lines of code.

The calls to v8::platform::PumpMessageLoop() are currently no-ops
because V8 does not (yet?) use v8::Platform::CallOnForegroundThread().

Packagers that link against a shared libv8 now also need to make
libv8_platform available.

PR-URL: #1329
Reviewed-By: Fedor Indutny <fedor@indutny.com>

configure

@@ -664,7 +664,7 @@ def configure_v8(o):
   if options.shared_v8_libname:
     o['libraries'] += ['-l%s' % options.shared_v8_libname]
   elif options.shared_v8:
-    o['libraries'] += ['-lv8']
+    o['libraries'] += ['-lv8', '-lv8_platform']
   if options.shared_v8_includes:
     o['include_dirs'] += [options.shared_v8_includes]
 

node.gyp

@@ -108,7 +108,6 @@
         'src/node_main.cc',
         'src/node_os.cc',
         'src/node_v8.cc',
-        'src/node_v8_platform.cc',
         'src/node_stat_watcher.cc',
         'src/node_watchdog.cc',
         'src/node_zlib.cc',
@@ -312,7 +311,12 @@
             'deps/v8/include/v8.h',
             'deps/v8/include/v8-debug.h',
           ],
-          'dependencies': [ 'deps/v8/tools/gyp/v8.gyp:v8' ],
+          'dependencies': [
+            'deps/v8/tools/gyp/v8.gyp:v8',
+            'deps/v8/tools/gyp/v8.gyp:v8_libplatform',
+          ],
+          # libplatform/libplatform.h includes include/v8platform.h
+          'include_dirs': [ 'deps/v8' ],
         }],
 
         [ 'node_shared_zlib=="false"', {

src/node.cc

@@ -5,7 +5,6 @@
 #include "node_http_parser.h"
 #include "node_javascript.h"
 #include "node_version.h"
-#include "node_v8_platform.h"
 
 #if defined HAVE_PERFCTR
 #include "node_counters.h"
@@ -38,6 +37,7 @@
 #include "string_bytes.h"
 #include "util.h"
 #include "uv.h"
+#include "libplatform/libplatform.h"
 #include "v8-debug.h"
 #include "v8-profiler.h"
 #include "zlib.h"
@@ -140,6 +140,7 @@ static bool debugger_running;
 static uv_async_t dispatch_debug_messages_async;
 
 static Isolate* node_isolate = nullptr;
+static v8::Platform* default_platform;
 
 class ArrayBufferAllocator : public ArrayBuffer::Allocator {
  public:
@@ -3824,8 +3825,11 @@ static void StartNodeInstance(void* arg) {
 
     bool more;
     do {
+      v8::platform::PumpMessageLoop(default_platform, isolate);
       more = uv_run(env->event_loop(), UV_RUN_ONCE);
+
       if (more == false) {
+        v8::platform::PumpMessageLoop(default_platform, isolate);
         EmitBeforeExit(env);
 
         // Emit `beforeExit` if the loop became alive either after emitting
@@ -3872,7 +3876,9 @@ int Start(int argc, char** argv) {
   V8::SetEntropySource(crypto::EntropySource);
 #endif
 
-  V8::InitializePlatform(new Platform(4));
+  const int thread_pool_size = 4;
+  default_platform = v8::platform::CreateDefaultPlatform(thread_pool_size);
+  V8::InitializePlatform(default_platform);
   V8::Initialize();
 
   int exit_code = 1;
@@ -3889,6 +3895,9 @@ int Start(int argc, char** argv) {
   }
   V8::Dispose();
 
+  delete default_platform;
+  default_platform = nullptr;
+
   delete[] exec_argv;
   exec_argv = nullptr;