[extensions] added checks that function is not empty

extensions/renderer/module_system.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "extensions/renderer/module_system.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/macros.h"
@@ skipping 291 matching lines @@
                module_name,
                "method_name",
                method_name);
 
   v8::EscapableHandleScope handle_scope(GetIsolate());
   v8::Local<v8::Context> v8_context = context()->v8_context();
   v8::Context::Scope context_scope(v8_context);
 
   v8::Local<v8::Function> function =
       GetModuleFunction(module_name, method_name);
+  if (function.IsEmpty()) {

[Devlin, 2016/12/01 22:09:47]

This *shouldn't* ever happen, but I wouldn't be entirely surprised if it were. 
Can we NOTREACHED here (and below)?

[kozy, 2016/12/01 22:19:25]

Done.

+    return handle_scope.Escape(v8::Undefined(GetIsolate()));
+  }
 
   v8::Local<v8::Value> result;
   {
     v8::TryCatch try_catch(GetIsolate());
     try_catch.SetCaptureMessage(true);
     result = context_->CallFunction(function, argc, argv);
     if (try_catch.HasCaught()) {
       HandleException(try_catch);
       result = v8::Undefined(GetIsolate());
     }
@@ skipping 21 matching lines @@
                                         v8::Local<v8::Value> argv[]) {
   TRACE_EVENT2("v8", "v8.callModuleMethodSafe", "module_name", module_name,
                "method_name", method_name);
 
   v8::HandleScope handle_scope(GetIsolate());
   v8::Local<v8::Context> v8_context = context()->v8_context();
   v8::Context::Scope context_scope(v8_context);
 
   v8::Local<v8::Function> function =
       GetModuleFunction(module_name, method_name);
+  if (function.IsEmpty()) {
+    return;
+  }
 
   {
     v8::TryCatch try_catch(GetIsolate());
     try_catch.SetCaptureMessage(true);
     context_->SafeCallFunction(function, argc, argv);
     if (try_catch.HasCaught())
       HandleException(try_catch);
   }
 }
 
@@ skipping 452 matching lines @@
       !value->IsFunction()) {
     Fatal(context_, module_name + "." + method_name + " is not a function");
     return function;
   }
 
   function = v8::Local<v8::Function>::Cast(value);
   return function;
 }
 
 }  // namespace extensions