[Extensions Bindings] Allow custom hooks to return values, throw

extensions/renderer/api_binding.cc

Index: extensions/renderer/api_binding.cc
diff --git a/extensions/renderer/api_binding.cc b/extensions/renderer/api_binding.cc
index 218565b17821ff57a41e2f1f326a45db8787312b..e10886f4f7107bdd87793c472ac2656ba03143a4 100644
--- a/extensions/renderer/api_binding.cc
+++ b/extensions/renderer/api_binding.cc
@@ -210,9 +210,10 @@ void APIBinding::HandleCall(const std::string& name,
     v8::TryCatch try_catch(isolate);
     APIBindingHooks::RequestResult hooks_result =
         APIBindingHooks::RequestResult::NOT_HANDLED;
+    v8::Local<v8::Value> return_value;
     hooks_result = binding_hooks_->HandleRequest(api_name_, name, context,
                                                  signature, &argument_list,
-                                                 *type_refs_);
+                                                 *type_refs_, &return_value);
 
     switch (hooks_result) {
       case APIBindingHooks::RequestResult::INVALID_INVOCATION:
@@ -224,6 +225,8 @@ void APIBinding::HandleCall(const std::string& name,
         try_catch.ReThrow();
         return;
       case APIBindingHooks::RequestResult::HANDLED:
+        if (!return_value.IsEmpty())

[jbroman, 2017/01/02 20:05:46]

Do we expect this to ever be IsEmpty is a case that shouldn't be a DCHECK
failure (i.e. a programming failure)?

Every JS function returns a value, even if it's |undefined|.

[Devlin, 2017/01/04 18:38:07]

In the case of a native (c++) handler hook without a return value, I'd expect
this to happen.

+          arguments->Return(return_value);
         return;  // Our work here is done.
       case APIBindingHooks::RequestResult::NOT_HANDLED:
         break;  // Handle in the default manner.