[d8 Workers] Add max worker count, throw an exception if too many.

src/d8.cc

Index: src/d8.cc
diff --git a/src/d8.cc b/src/d8.cc
index 5fa7c262994c77076951bf97022d00e2c0119731..246c8f038c33920b5595b3f1c979566c135ee99c 100644
--- a/src/d8.cc
+++ b/src/d8.cc
@@ -75,6 +75,7 @@ namespace v8 {
 namespace {
 
 const int MB = 1024 * 1024;
+const int kMaxWorkers = 50;
 
 
 class ShellArrayBufferAllocator : public v8::ArrayBuffer::Allocator {
@@ -706,6 +707,11 @@ void Shell::WorkerNew(const v8::FunctionCallbackInfo<v8::Value>& args) {
 
   {
     base::LockGuard<base::Mutex> lock_guard(workers_mutex_.Pointer());
+    if (workers_.length() >= kMaxWorkers) {
+      Throw(args.GetIsolate(), "Too many workers, I won't let you create more");
+      return;
+    }
+
     // Initialize the internal field to NULL; if we return early without
     // creating a new Worker (because the main thread is terminating) we can
     // early-out from the instance calls.