Replace OS::NumberOfCores() with CPU::NumberOfProcessorsOnline().

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index 774ad5ca5647271853a94320bb8be2d58b887765..54329b7b98e583acf32548d974a3a66334d8cb3c 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -137,7 +137,7 @@ v8::TryCatch* ThreadLocalTop::TryCatchHandler() {
 
 int SystemThreadManager::NumberOfParallelSystemThreads(
     ParallelSystemComponent type) {
-  int number_of_threads = Min(OS::NumberOfCores(), kMaxThreads);
+  int number_of_threads = Min(CPU::NumberOfProcessorsOnline(), kMaxThreads);
   ASSERT(number_of_threads > 0);
   if (number_of_threads ==  1) {
     return 0;