Add numHeapSpaces to isolate

ext/v8/isolate.cc

@@ -10,7 +10,8 @@ namespace rr {
       defineSingletonMethod("New", &New).
 
       defineMethod("Dispose", &Isolate::Dispose).
-      defineMethod("Equals", &rr::Isolate::PointerEquals).
+      defineMethod("Equals", &Isolate::PointerEquals).
+      defineMethod("NumberOfHeapSpaces", &Isolate::NumberOfHeapSpaces).
 
       store(&Class);
   }
@@ -38,6 +39,12 @@ namespace rr {
     return Qnil;
   }
 
+  VALUE Isolate::NumberOfHeapSpaces(VALUE self) {
+    Isolate isolate(self);
+    size_t spaces = isolate->NumberOfHeapSpaces();
+    return SIZET2NUM(spaces);
+  }
+
   template <>
   void Pointer<v8::Isolate>::unwrap(VALUE value) {
     Data_Get_Struct(value, class v8::Isolate, pointer);

ext/v8/isolate.h

@@ -127,6 +127,8 @@ namespace rr {
 
     static VALUE Dispose(VALUE self);
 
+    static VALUE NumberOfHeapSpaces(VALUE self);
+
     /**
      * Recent versions of V8 will segfault unless you pass in an
      * ArrayBufferAllocator into the create params of an isolate. This

spec/c/isolate_spec.rb

@@ -15,4 +15,8 @@
   it "can be disposed of" do
     isolate.Dispose()
   end
+
+  it "has has heap spaces" do
+    expect(isolate.NumberOfHeapSpaces()).to be >= 1
+  end
 end