Mojo: Log an error when we fail to find a JS module.

gin/modules/module_runner_delegate.cc

Index: gin/modules/module_runner_delegate.cc
diff --git a/gin/modules/module_runner_delegate.cc b/gin/modules/module_runner_delegate.cc
index 16b5afd0303ba8a8819cbe54aef25ec8c4c24a84..d00c2774ffddcc18922d203682f5b52bbd09c0f0 100644
--- a/gin/modules/module_runner_delegate.cc
+++ b/gin/modules/module_runner_delegate.cc
@@ -11,11 +11,15 @@
 namespace gin {
 
 ModuleRunnerDelegate::ModuleRunnerDelegate(
-  const std::vector<base::FilePath>& search_paths)
+    const std::vector<base::FilePath>& search_paths)
     : module_provider_(search_paths) {
+  module_provider_.set_completion_callback(
+      base::Bind(&ModuleRunnerDelegate::DidLoadFileModules,
+                 base::Unretained(this)));
 }
 
 ModuleRunnerDelegate::~ModuleRunnerDelegate() {
+  module_provider_.reset_completion_callback();
 }
 
 void ModuleRunnerDelegate::AddBuiltinModule(const std::string& id,
@@ -27,8 +31,8 @@ void ModuleRunnerDelegate::AttemptToLoadMoreModules(Runner* runner) {
   ModuleRegistry* registry = ModuleRegistry::From(
       runner->GetContextHolder()->context());
   registry->AttemptToLoadMoreModules(runner->GetContextHolder()->isolate());
-  module_provider_.AttempToLoadModules(
-      runner, registry->unsatisfied_dependencies());
+  unsatisfied_dependencies_ = registry->unsatisfied_dependencies();
+  module_provider_.AttemptToLoadModules(runner, unsatisfied_dependencies_);
 }
 
 v8::Handle<v8::ObjectTemplate> ModuleRunnerDelegate::GetGlobalTemplate(
@@ -56,4 +60,17 @@ void ModuleRunnerDelegate::DidRunScript(ShellRunner* runner) {
   AttemptToLoadMoreModules(runner);
 }
 
+void ModuleRunnerDelegate::DidLoadFileModules(
+    const std::set<std::string>& loaded_modules) {
+  std::set<std::string> failed_modules;
+  std::set_difference(
+      unsatisfied_dependencies_.begin(), unsatisfied_dependencies_.end(),
+      loaded_modules.begin(), loaded_modules.end(),
+      std::inserter(failed_modules, failed_modules.end()));
+  for (std::set<std::string>::const_iterator it = failed_modules.begin();
+       it != failed_modules.end(); ++it) {
+    LOG(ERROR) << "Failed to load module: " << *it;
+  }
+}
+
 }  // namespace gin