6 files changed, 49 insertions, 13 deletions
diff --git a/chrome/renderer/extensions/bindings_utils.cc b/chrome/renderer/extensions/bindings_utils.cc
index 13deb2a..d96f8d7 100644
--- a/chrome/renderer/extensions/bindings_utils.cc
+++ b/chrome/renderer/extensions/bindings_utils.cc
@@ -13,6 +13,7 @@ using WebKit::WebFrame;
 namespace bindings_utils {
 
 const char* kChromeHidden = "chromeHidden";
+const char* kValidateCallbacks = "validateCallbacks";
 
 struct SingletonData {
   ContextList contexts;
@@ -40,6 +41,13 @@ v8::Handle<v8::Value> ExtensionBase::GetChromeHidden(
   if (hidden.IsEmpty() || hidden->IsUndefined()) {
     hidden = v8::Object::New();
     global->SetHiddenValue(v8::String::New(kChromeHidden), hidden);
+
+#ifdef _DEBUG
+    // Tell extension_process_bindings.js to validate callbacks and events
+    // against their schema definitions in api/extension_api.json.
+    v8::Local<v8::Object>::Cast(hidden)
+        ->Set(v8::String::New(kValidateCallbacks), v8::True());
+#endif
   }
 
   DCHECK(hidden->IsObject());
@@ -94,9 +102,9 @@ RenderView* GetRenderViewForCurrentContext() {
   return renderview;
 }
 
-void CallFunctionInContext(v8::Handle<v8::Context> context,
-                           const std::string& function_name, int argc,
-                           v8::Handle<v8::Value>* argv) {
+v8::Handle<v8::Value> CallFunctionInContext(v8::Handle<v8::Context> context,
+    const std::string& function_name, int argc,
+    v8::Handle<v8::Value>* argv) {
   v8::Context::Scope context_scope(context);
 
   // Look up the function name, which may be a sub-property like
@@ -111,12 +119,14 @@ void CallFunctionInContext(v8::Handle<v8::Context> context,
   }
   if (value.IsEmpty() || !value->IsFunction()) {
     NOTREACHED();
-    return;
+    return v8::Undefined();
   }
 
   v8::Local<v8::Function> function = v8::Local<v8::Function>::Cast(value);
   if (!function.IsEmpty())
-    function->Call(v8::Object::New(), argc, argv);
+    return function->Call(v8::Object::New(), argc, argv);
+
+  return v8::Undefined();
 }
 
 }  // namespace bindings_utils
diff --git a/chrome/renderer/extensions/bindings_utils.h b/chrome/renderer/extensions/bindings_utils.h
index 604cb2c..7354c72 100644
--- a/chrome/renderer/extensions/bindings_utils.h
+++ b/chrome/renderer/extensions/bindings_utils.h
@@ -106,10 +106,12 @@ RenderView* GetRenderViewForCurrentContext();
 
 // Call the named javascript function with the given arguments in a context.
 // The function name should be reachable from the chromeHidden object, and can
-// be a sub-property like "Port.dispatchOnMessage".
-void CallFunctionInContext(v8::Handle<v8::Context> context,
-                           const std::string& function_name, int argc,
-                           v8::Handle<v8::Value>* argv);
+// be a sub-property like "Port.dispatchOnMessage". Returns the result of 
+// the function call. If an exception is thrown an empty Handle will be
+// returned.
+v8::Handle<v8::Value> CallFunctionInContext(v8::Handle<v8::Context> context,
+    const std::string& function_name, int argc,
+    v8::Handle<v8::Value>* argv);
 
 }  // namespace bindings_utils
 
diff --git a/chrome/renderer/extensions/event_bindings.cc b/chrome/renderer/extensions/event_bindings.cc
index 5003b82..b2cecdc 100644
--- a/chrome/renderer/extensions/event_bindings.cc
+++ b/chrome/renderer/extensions/event_bindings.cc
@@ -287,6 +287,17 @@ void EventBindings::CallFunction(const std::string& function_name,
        it != GetContexts().end(); ++it) {
     if (render_view && render_view != (*it)->render_view)
       continue;
-    CallFunctionInContext((*it)->context, function_name, argc, argv);
+    v8::Handle<v8::Value> retval = CallFunctionInContext((*it)->context,
+        function_name, argc, argv);
+    // In debug, the js will validate the event parameters and return a 
+    // string if a validation error has occured.
+    // TODO(rafaelw): Consider only doing this check if function_name ==
+    // "Event.dispatchJSON".
+#ifdef _DEBUG
+    if (!retval.IsEmpty() && !retval->IsUndefined()) {
+      std::string error = *v8::String::AsciiValue(retval);
+      DCHECK(false) << error;
+    }
+#endif
   }
 }
diff --git a/chrome/renderer/extensions/event_bindings.h b/chrome/renderer/extensions/event_bindings.h
index 022fe09..736cb8a 100644
--- a/chrome/renderer/extensions/event_bindings.h
+++ b/chrome/renderer/extensions/event_bindings.h
@@ -35,6 +35,8 @@ class EventBindings {
   // events.  If render_view is non-NULL, only call the function in contexts
   // belonging to that view.  See comments on
   // bindings_utils::CallFunctionInContext for more details.
+  // The called javascript function should not return a value other than
+  // v8::Undefined(). A DCHECK is setup to break if it is otherwise.
   static void CallFunction(const std::string& function_name, int argc,
                            v8::Handle<v8::Value>* argv,
                            RenderView* render_view);
diff --git a/chrome/renderer/extensions/extension_api_client_unittest.cc b/chrome/renderer/extensions/extension_api_client_unittest.cc
index 49136c5..d5f73bb 100644
--- a/chrome/renderer/extensions/extension_api_client_unittest.cc
+++ b/chrome/renderer/extensions/extension_api_client_unittest.cc
@@ -71,7 +71,9 @@ TEST_F(ExtensionAPIClientTest, CallbackDispatching) {
     "}"
     "function callback(result) {"
     "  assert(typeof result == 'object', 'result not object');"
-    "  assert(JSON.stringify(result) == '{\"foo\":\"bar\"}', "
+    "  assert(JSON.stringify(result) == '{\"id\":1,\"index\":1,\"windowId\":1,"
+                                        "\"selected\":true,"
+                                        "\"url\":\"http://www.google.com/\"}',"
     "         'incorrect result');"
     "  console.log('pass')"
     "}"
@@ -92,7 +94,8 @@ TEST_F(ExtensionAPIClientTest, CallbackDispatching) {
 
   // Now send the callback a response
   ExtensionProcessBindings::HandleResponse(
-      callback_id, true, "{\"foo\":\"bar\"}", "");
+    callback_id, true, "{\"id\":1,\"index\":1,\"windowId\":1,\"selected\":true,"
+                       "\"url\":\"http://www.google.com/\"}", "");
 
   // And verify that it worked
   ASSERT_EQ("pass", GetConsoleMessage());
diff --git a/chrome/renderer/extensions/extension_process_bindings.cc b/chrome/renderer/extensions/extension_process_bindings.cc
index 8d07d82..d28adb0 100644
--- a/chrome/renderer/extensions/extension_process_bindings.cc
+++ b/chrome/renderer/extensions/extension_process_bindings.cc
@@ -298,8 +298,16 @@ void ExtensionProcessBindings::HandleResponse(int request_id, bool success,
   argv[2] = v8::Boolean::New(success);
   argv[3] = v8::String::New(response.c_str());
   argv[4] = v8::String::New(error.c_str());
-  bindings_utils::CallFunctionInContext(
+  v8::Handle<v8::Value> retval = bindings_utils::CallFunctionInContext(
       request->second->context, "handleResponse", arraysize(argv), argv);
+  // In debug, the js will validate the callback parameters and return a 
+  // string if a validation error has occured.
+#ifdef _DEBUG
+  if (!retval.IsEmpty() && !retval->IsUndefined()) {
+    std::string error = *v8::String::AsciiValue(retval);
+    DCHECK(false) << error;
+  }
+#endif
 
   pending_requests.erase(request);
 }