DevTools: move front-end URL handling to DevToolsUIBindingds

BUG=662859

Review-Url: https://codereview.chromium.org/2607833002
Cr-Commit-Position: refs/heads/master@{#440926}
DevToolsUIBindings* DevToolsUIBindings::ForWebContents(
     content::WebContents* web_contents) {
 if (g_instances == NULL)
   return NULL;
 DevToolsUIBindingsList* instances = g_instances.Pointer();
 for (DevToolsUIBindingsList::iterator it(instances->begin());
      it != instances->end(); ++it) {
   if ((*it)->web_contents() == web_contents)
     return *it;
 }
 return NULL;
}

DevToolsUIBindings* DevToolsUIBindings::ForWebContents(
     content::WebContents* web_contents) {
 if (g_instances == NULL)
   return NULL;
 DevToolsUIBindingsList* instances = g_instances.Pointer();
 for (DevToolsUIBindingsList::iterator it(instances->begin());
      it != instances->end(); ++it) {
   if ((*it)->web_contents() == web_contents)
     return *it;
 }
 return NULL;
}
