Revert of [platform] Change default platform max thread pool size 4 -> 8

src/libplatform/default-platform.cc

Index: src/libplatform/default-platform.cc
diff --git a/src/libplatform/default-platform.cc b/src/libplatform/default-platform.cc
index 71ee6bee980372a17ac6d33e5e16e794e1aa21be..3d188f1841d13f17ffd3edaed0e35f94d471aca7 100644
--- a/src/libplatform/default-platform.cc
+++ b/src/libplatform/default-platform.cc
@@ -29,7 +29,9 @@
   return reinterpret_cast<DefaultPlatform*>(platform)->PumpMessageLoop(isolate);
 }
 
-const int DefaultPlatform::kMaxThreadPoolSize = 8;
+
+const int DefaultPlatform::kMaxThreadPoolSize = 4;
+
 
 DefaultPlatform::DefaultPlatform()
     : initialized_(false), thread_pool_size_(0) {}
@@ -64,7 +66,7 @@
   base::LockGuard<base::Mutex> guard(&lock_);
   DCHECK(thread_pool_size >= 0);
   if (thread_pool_size < 1) {
-    thread_pool_size = base::SysInfo::NumberOfProcessors() - 1;
+    thread_pool_size = base::SysInfo::NumberOfProcessors();
   }
   thread_pool_size_ =
       std::max(std::min(thread_pool_size, kMaxThreadPoolSize), 1);