Set up a field trial flag to prerender Instant search base url on omnibox focus event.

chrome/browser/ui/omnibox/omnibox_edit_model.cc

Index: chrome/browser/ui/omnibox/omnibox_edit_model.cc
diff --git a/chrome/browser/ui/omnibox/omnibox_edit_model.cc b/chrome/browser/ui/omnibox/omnibox_edit_model.cc
index 60bb805edf94296d762b2a98e8ed500ea1506854..5dbba78dc191504273090d90042d6f459014d12b 100644
--- a/chrome/browser/ui/omnibox/omnibox_edit_model.cc
+++ b/chrome/browser/ui/omnibox/omnibox_edit_model.cc
@@ -944,6 +944,10 @@ void OmniboxEditModel::OnSetFocus(bool control_down) {
         permanent_text_, base::string16::npos, base::string16(),
         delegate_->GetURL(), ClassifyPage(), false, false, true, true));
   }
+  // Prerender instant search base page.
+  if (chrome::ShouldPrerenderInstantSearchBaseOnFocus() &&
+      InstantSearchPrerenderer::GetForProfile(profile_))
+    delegate_->DoPrerender(AutocompleteMatch());

[kmadhusu, 2014/06/12 21:12:38]

We should not pass an new AutocompleteMatch() here. It makes me think may be
there is a better place to init InstantSearchPrerenderer. Can we do the
initialization in OmniboxCurrentPageDelegateImpl::OnFocusChanged()?

[sidharthms, 2014/06/12 23:33:34]

Moved to separate cl

 
   if (user_input_in_progress_ || !in_revert_)
     delegate_->OnInputStateChanged();