bindings: Add empty checks for toV8()

Source/web/WebDevToolsFrontendImpl.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 67 matching lines @@
     if (m_webFrame == frame) {
         v8::Isolate* isolate = v8::Isolate::GetCurrent();
         ScriptState* scriptState = ScriptState::forMainWorld(m_webFrame->frame());
         ScriptState::Scope scope(scriptState);
 
         if (m_devtoolsHost)
             m_devtoolsHost->disconnectClient();
         m_devtoolsHost = DevToolsHost::create(this, m_webFrame->frame());
         v8::Handle<v8::Object> global = scriptState->context()->Global();
         v8::Handle<v8::Value> devtoolsHostObj = toV8(m_devtoolsHost.get(), global, scriptState->isolate());
+        ASSERT(!devtoolsHostObj.IsEmpty());

[haraken, 2015/04/28 04:24:59]

Who guarantees this is not empty?

[bashi, 2015/04/28 05:41:53]

This is DevTool related code so I just guessed that this is not empty in
general. Adding yurys@ for his input.

         global->Set(v8AtomicString(isolate, "DevToolsHost"), devtoolsHostObj);
     }
 
     if (m_injectedScriptForOrigin.isEmpty())
         return;
 
     String origin = frame->securityOrigin().toString();
     String script = m_injectedScriptForOrigin.get(origin);
     if (script.isEmpty())
         return;
@@ skipping 27 matching lines @@
 {
     WebLocalFrameImpl::fromFrame(targetFrame)->viewImpl()->showContextMenuAtPoint(x, y, menuProvider);
 }
 
 void WebDevToolsFrontendImpl::setInjectedScriptForOrigin(const String& origin, const String& source)
 {
     m_injectedScriptForOrigin.set(origin, source);
 }
 
 } // namespace blink