Fix more GC unsafe places

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index 91ecc41486466e06db4e57d6743e9914a1ca74db..5f480c9073fac29c43ed90b0e7f84f01ea155ad8 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -2658,8 +2658,9 @@ void v8::Object::SetIndexedPropertiesToPixelData(uint8_t* data, int length) {
     return;
   }
   i::Handle<i::PixelArray> pixels = i::Factory::NewPixelArray(length, data);
-  self->set_map(
-      *i::Factory::GetSlowElementsMap(i::Handle<i::Map>(self->map())));
+  i::Handle<i::Map> slow_map =
+      i::Factory::GetSlowElementsMap(i::Handle<i::Map>(self->map()));
+  self->set_map(*slow_map);
   self->set_elements(*pixels);
 }
 
@@ -2713,8 +2714,9 @@ void v8::Object::SetIndexedPropertiesToExternalArrayData(
   }
   i::Handle<i::ExternalArray> array =
       i::Factory::NewExternalArray(length, array_type, data);
-  self->set_map(
-      *i::Factory::GetSlowElementsMap(i::Handle<i::Map>(self->map())));
+  i::Handle<i::Map> slow_map =
+      i::Factory::GetSlowElementsMap(i::Handle<i::Map>(self->map()));
+  self->set_map(*slow_map);
   self->set_elements(*array);
 }