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

extensions/renderer/api_binding_hooks.h

Index: extensions/renderer/api_binding_hooks.h
diff --git a/extensions/renderer/api_binding_hooks.h b/extensions/renderer/api_binding_hooks.h
index d6620275017e656fc0182af51f7fdc2d69d78c12..e53b632c57499c50d774eef38123425b099ddf7d 100644
--- a/extensions/renderer/api_binding_hooks.h
+++ b/extensions/renderer/api_binding_hooks.h
@@ -30,11 +30,21 @@ class APISignature;
 class APIBindingHooks {
  public:
   // The result of checking for hooks to handle a request.
-  enum class RequestResult {
-    HANDLED,             // A custom hook handled the request.
-    THROWN,              // An exception was thrown during parsing or handling.
-    INVALID_INVOCATION,  // The request was called with invalid arguments.
-    NOT_HANDLED,         // The request was not handled.
+  struct RequestResult {
+    enum ResultCode {
+      HANDLED,             // A custom hook handled the request.
+      THROWN,              // An exception was thrown during parsing or
+                           // handling.
+      INVALID_INVOCATION,  // The request was called with invalid arguments.
+      NOT_HANDLED,         // The request was not handled.
+    };
+
+    explicit RequestResult(ResultCode code);
+    RequestResult(const RequestResult& other);
+    ~RequestResult();

[jbroman, 2017/01/04 21:57:49]

Is the [chromium-style] plugin forcing these to be out-of-line? If not, then the
first can be inline and the other two are implied (v8::Local is trivial to copy
and destroy -- it's just a pointer internally).

[Devlin, 2017/01/04 23:29:29]

Yeah, this was the result of being bullied by [chromium-style].

+
+    ResultCode code;
+    v8::Local<v8::Value> return_value;  // Only valid if code == HANDLED.
   };
 
   // The callback to handle an API method. We pass in the expected signature
@@ -68,8 +78,8 @@ class APIBindingHooks {
                            const std::string& api_name);
 
   // Looks for a custom hook to handle the given request and, if one exists,
-  // runs it. Returns the result of trying to run the hook, or NOT_HANDLED if no
-  // hook was found.
+  // runs it. Returns the result of running the hook, if any. Populates

[jbroman, 2017/01/04 21:57:49]

If the |return_value| argument is removed, then this last bit of comment can go
away.

[Devlin, 2017/01/04 23:29:29]

Whoops, done.

+  // |return_value| with a value to return, if any.
   RequestResult HandleRequest(const std::string& api_name,
                               const std::string& method_name,
                               v8::Local<v8::Context> context,