Split out libplatform into a separate libary

src/d8.cc

Index: src/d8.cc
diff --git a/src/d8.cc b/src/d8.cc
index 8bdf26f4c27bbb4bd063196b0be3ad76d6552d6f..33d3a2a0087fd1b61c253888eeb4b2f6132d6690 100644
--- a/src/d8.cc
+++ b/src/d8.cc
@@ -35,6 +35,7 @@
 
 #include "src/d8.h"
 
+#include "include/libplatform/libplatform.h"
 #ifndef V8_SHARED
 #include "src/api.h"
 #include "src/base/cpu.h"
@@ -1549,6 +1550,9 @@ class StartupDataHandler {
 int Shell::Main(int argc, char* argv[]) {
   if (!SetOptions(argc, argv)) return 1;
   v8::V8::InitializeICU(options.icu_data_file);
+  v8::Platform* platform =
+      v8::platform::CreateDefaultPlatform(base::OS::NumberOfProcessorsOnline());
+  v8::V8::InitializePlatform(platform);
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
   StartupDataHandler startup_data(options.natives_blob, options.snapshot_blob);
 #endif
@@ -1626,6 +1630,8 @@ int Shell::Main(int argc, char* argv[]) {
   }
   isolate->Dispose();
   V8::Dispose();
+  V8::ShutdownPlatform();
+  delete platform;
 
   OnExit();