Merge pull request #19 from electron/get-wrapper-const

GetWrapper should be const

native_mate/wrappable.cc

@@ -23,7 +23,7 @@ WrappableBase::~WrappableBase() {
   wrapper_.Reset();
 }
 
-v8::Local<v8::Object> WrappableBase::GetWrapper() {
+v8::Local<v8::Object> WrappableBase::GetWrapper() const {
   if (!wrapper_.IsEmpty())
     return v8::Local<v8::Object>::New(isolate_, wrapper_);
   else

native_mate/wrappable_base.h

@@ -31,7 +31,7 @@ class WrappableBase {
   virtual ~WrappableBase();
 
   // Retrieve the v8 wrapper object cooresponding to this object.
-  v8::Local<v8::Object> GetWrapper();
+  v8::Local<v8::Object> GetWrapper() const;
 
   // Returns the Isolate this object is created in.
   v8::Isolate* isolate() const { return isolate_; }