Ensure there is some space on JS stack available for bootstrapping.

Review URL: https://codereview.chromium.org/1203873005

Cr-Commit-Position: refs/heads/master@{#29256}

src/bootstrapper.cc

@@ -1541,7 +1541,7 @@ bool Genesis::CompileNative(Isolate* isolate, Vector<const char> name,
   // environment has been at least partially initialized. Add a stack check
   // before entering JS code to catch overflow early.
   StackLimitCheck check(isolate);
-  if (check.HasOverflowed()) {
+  if (check.JsHasOverflowed(1 * KB)) {
     isolate->StackOverflow();
     return false;
   }

src/isolate.cc

@@ -2772,15 +2772,15 @@ void Isolate::CheckDetachedContextsAfterGC() {
 }
 
 
-bool StackLimitCheck::JsHasOverflowed() const {
+bool StackLimitCheck::JsHasOverflowed(uintptr_t gap) const {
   StackGuard* stack_guard = isolate_->stack_guard();
 #ifdef USE_SIMULATOR
   // The simulator uses a separate JS stack.
   Address jssp_address = Simulator::current(isolate_)->get_sp();
   uintptr_t jssp = reinterpret_cast<uintptr_t>(jssp_address);
-  if (jssp < stack_guard->real_jslimit()) return true;
+  if (jssp - gap < stack_guard->real_jslimit()) return true;
 #endif  // USE_SIMULATOR
-  return GetCurrentStackPosition() < stack_guard->real_climit();
+  return GetCurrentStackPosition() - gap < stack_guard->real_climit();
 }
 
 

src/isolate.h

@@ -1481,7 +1481,7 @@ class StackLimitCheck BASE_EMBEDDED {
   }
 
   // Use this to check for stack-overflow when entering runtime from JS code.
-  bool JsHasOverflowed() const;
+  bool JsHasOverflowed(uintptr_t gap = 0) const;
 
  private:
   Isolate* isolate_;