Skip GetNewBrowserInfo call for PDF renderer processes (see issue #3047)

With PdfUnseasoned the PDF file will be loaded in a dedicated renderer process.
We identify this process by adding the kPdfRenderer command-line flag (similar
to how kExtensionProcess is used to identify an extension renderer process). We
then avoid calling GetNewBrowserInfo for the PDF renderer process because we
know the request will otherwise time out.

libcef/renderer/alloy/alloy_content_renderer_client.cc

@@ -110,16 +110,6 @@
 #include "base/strings/sys_string_conversions.h"
 #endif
 
-namespace {
-
-bool IsStandaloneExtensionProcess() {
-  return extensions::ExtensionsEnabled() &&
-         extensions::CefExtensionsRendererClient::
-             IsStandaloneExtensionProcess();
-}
-
-}  // namespace
-
 AlloyContentRendererClient::AlloyContentRendererClient()
     : main_entry_time_(base::TimeTicks::Now()),
       render_manager_(new CefRenderManager) {
@@ -200,7 +190,7 @@ void AlloyContentRendererClient::RenderThreadStarted() {
 
   content::RenderThread* thread = content::RenderThread::Get();
 
-  const bool is_extension = IsStandaloneExtensionProcess();
+  const bool is_extension = CefRenderManager::IsExtensionProcess();
 
   thread->SetRendererProcessType(
       is_extension