Cleanup: Move kAboutScheme constant into content namespace.

content/renderer/render_frame_impl.cc

Index: content/renderer/render_frame_impl.cc
diff --git a/content/renderer/render_frame_impl.cc b/content/renderer/render_frame_impl.cc
index 6200b3480aa2e5a38f255e3c412fc817cb30a73f..647d32563aa9838d9de937abafad1e65f8bb62f1 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -2543,8 +2543,7 @@ WebNavigationPolicy RenderFrameImpl::DecidePolicyForNavigation(
   // browser process, and issue a special POST navigation in WebKit (via
   // FrameLoader::loadFrameRequest). See ResourceDispatcher and WebURLLoaderImpl
   // for examples of how to send the httpBody data.
-  if (!frame->parent() && is_content_initiated &&
-      !url.SchemeIs(chrome::kAboutScheme)) {
+  if (!frame->parent() && is_content_initiated && !url.SchemeIs(kAboutScheme)) {
     bool send_referrer = false;
 
     // All navigations to or from WebUI URLs or within WebUI-enabled