Allow non default prefetch suggestions to be prefetched

chrome/browser/ui/omnibox/omnibox_controller.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/omnibox/omnibox_controller.h"
 
 #include "base/metrics/histogram.h"
 #include "chrome/browser/autocomplete/autocomplete_classifier.h"
 #include "chrome/browser/autocomplete/autocomplete_match.h"
 #include "chrome/browser/autocomplete/search_provider.h"
@@ skipping 12 matching lines @@
 #include "extensions/common/constants.h"
 #include "ui/gfx/rect.h"
 
 namespace {
 
 // Returns the AutocompleteMatch that the InstantController should prefetch, if
 // any.
 //
 // The SearchProvider may mark some suggestions to be prefetched based on
 // instructions from the suggest server. If such a match ranks sufficiently
-// highly, we'll return it.
+// highly or if kAllowPrefetchNonDefaultMatch field trial is enabled, we'll
+// return it.
 //
-// We only care about matches that are the default or the very first entry in
-// the dropdown (which can happen for non-default matches only if we're hiding
-// a top verbatim match) or the second entry in the dropdown (which can happen
-// for non-default matches when a top verbatim match is shown); for other
-// matches, we think the likelihood of the user selecting them is low enough
-// that prefetching isn't worth doing.
+// If the kAllowPrefetchNonDefaultMatch field trial is enabled we return the
+// prefetch suggestion even if it is not the default match. Otherwise we only
+// care about matches that are the default or the very first entry in the
+// dropdown (which can happen for non-default matches only if we're hiding a top
+// verbatim match) or the second entry in the dropdown (which can happen for
+// non-default matches when a top verbatim match is shown); for other matches,
+// we think the likelihood of the user selecting them is low enough that
+// prefetching isn't worth doing.
 const AutocompleteMatch* GetMatchToPrefetch(const AutocompleteResult& result) {
-  // If the default match should be prefetched, do that.
-  const AutocompleteResult::const_iterator default_match(
-      result.default_match());
-  if ((default_match != result.end()) &&
-      SearchProvider::ShouldPrefetch(*default_match))
-    return &(*default_match);
+  if (chrome::ShouldAllowPrefetchNonDefaultMatch()) {
+    const AutocompleteResult::const_iterator prefetch_match = std::find_if(
+        result.begin(), result.end(), SearchProvider::ShouldPrefetch);
+    return prefetch_match != result.end() ? &(*prefetch_match) : NULL;
+  } else {

[Peter Kasting, 2014/06/19 23:03:09]

Nit: No else after return.

[sidharthms, 2014/06/20 00:30:49]

Done.

+    // If the default match should be prefetched, do that.
+    const AutocompleteResult::const_iterator default_match(
+        result.default_match());
+    if ((default_match != result.end()) &&
+        SearchProvider::ShouldPrefetch(*default_match))
+      return &(*default_match);
 
-  // Otherwise, if the top match is a verbatim match and the very next match is
-  // prefetchable, fetch that.
-  if ((result.ShouldHideTopMatch() ||
-       result.TopMatchIsStandaloneVerbatimMatch()) &&
-      (result.size() > 1) &&
-      SearchProvider::ShouldPrefetch(result.match_at(1)))
-    return &result.match_at(1);
+    // Otherwise, if the top match is a verbatim match and the very next match
+    // is prefetchable, fetch that.
+    if ((result.ShouldHideTopMatch() ||
+         result.TopMatchIsStandaloneVerbatimMatch()) &&
+        (result.size() > 1) &&
+        SearchProvider::ShouldPrefetch(result.match_at(1)))
+      return &result.match_at(1);
 
-  return NULL;
+    return NULL;
+  }
 }
 
 }  // namespace
 
 OmniboxController::OmniboxController(OmniboxEditModel* omnibox_edit_model,
                                      Profile* profile)
     : omnibox_edit_model_(omnibox_edit_model),
       profile_(profile),
       popup_(NULL),
       autocomplete_controller_(new AutocompleteController(profile, this,
           AutocompleteClassifier::kDefaultOmniboxProviders)) {
 }
 
 OmniboxController::~OmniboxController() {
 }
 
 void OmniboxController::StartAutocomplete(
     const AutocompleteInput& input) const {
   ClearPopupKeywordMode();
   popup_->SetHoveredLine(OmniboxPopupModel::kNoMatch);
 
   // We don't explicitly clear OmniboxPopupModel::manually_selected_match, as
   // Start ends up invoking OmniboxPopupModel::OnResultChanged which clears it.
   autocomplete_controller_->Start(input);
 }
 
 void OmniboxController::OnResultChanged(bool default_match_changed) {
   const bool was_open = popup_->IsOpen();
+  const AutocompleteResult& result = this->result();

[Peter Kasting, 2014/06/19 23:03:09]

Nit: I think it would be better to remove this and use result() below as needed.

[sidharthms, 2014/06/20 00:30:49]

Done.

   if (default_match_changed) {
     // The default match has changed, we need to let the OmniboxEditModel know
     // about new inline autocomplete text (blue highlight).
-    const AutocompleteResult& result = this->result();
     const AutocompleteResult::const_iterator match(result.default_match());
     if (match != result.end()) {
       current_match_ = *match;
       if (!prerender::IsOmniboxEnabled(profile_))
         DoPreconnect(*match);
       omnibox_edit_model_->OnCurrentMatchChanged();
-
-      if (chrome::IsInstantExtendedAPIEnabled()) {
-        InstantSuggestion prefetch_suggestion;
-        const AutocompleteMatch* match_to_prefetch = GetMatchToPrefetch(result);
-        if (match_to_prefetch) {
-          prefetch_suggestion.text = match_to_prefetch->contents;
-          prefetch_suggestion.metadata =
-              SearchProvider::GetSuggestMetadata(*match_to_prefetch);
-        }
-        // Send the prefetch suggestion unconditionally to the InstantPage. If
-        // there is no suggestion to prefetch, we need to send a blank query to
-        // clear the prefetched results.
-        omnibox_edit_model_->SetSuggestionToPrefetch(prefetch_suggestion);
-      }
     } else {
       InvalidateCurrentMatch();
       popup_->OnResultChanged();
       omnibox_edit_model_->OnPopupDataChanged(base::string16(), NULL,
                                               base::string16(), false);
     }
   } else {
     popup_->OnResultChanged();
   }
 
   if (!popup_->IsOpen() && was_open) {
     // Accept the temporary text as the user text, because it makes little sense
     // to have temporary text when the popup is closed.
     omnibox_edit_model_->AcceptTemporaryTextAsUserText();
   }
+
+  if (!chrome::IsInstantExtendedAPIEnabled())

[Peter Kasting, 2014/06/19 23:03:08]

Nit: Why not include this in the next conditional (if necessary, making that
conditional be an early-return)?

[sidharthms, 2014/06/20 00:30:49]

Done.

+    return;
+  if ((default_match_changed && result.default_match() != result.end()) ||
+      (chrome::ShouldAllowPrefetchNonDefaultMatch() && !result.empty())) {
+    InstantSuggestion prefetch_suggestion;
+    const AutocompleteMatch* match_to_prefetch = GetMatchToPrefetch(result);
+    if (match_to_prefetch) {
+      prefetch_suggestion.text = match_to_prefetch->contents;
+      prefetch_suggestion.metadata =
+          SearchProvider::GetSuggestMetadata(*match_to_prefetch);
+    }
+    // Send the prefetch suggestion unconditionally to the InstantPage. If
+    // there is no suggestion to prefetch, we need to send a blank query to
+    // clear the prefetched results.
+    omnibox_edit_model_->SetSuggestionToPrefetch(prefetch_suggestion);
+  }
 }
 
 void OmniboxController::InvalidateCurrentMatch() {
   current_match_ = AutocompleteMatch();
 }
 
 void OmniboxController::ClearPopupKeywordMode() const {
   if (popup_->IsOpen() &&
       popup_->selected_line_state() == OmniboxPopupModel::KEYWORD)
     popup_->SetSelectedLineState(OmniboxPopupModel::NORMAL);
 }
 
 void OmniboxController::DoPreconnect(const AutocompleteMatch& match) {
   if (!match.destination_url.SchemeIs(extensions::kExtensionScheme)) {
     // Warm up DNS Prefetch cache, or preconnect to a search service.
     UMA_HISTOGRAM_ENUMERATION("Autocomplete.MatchType", match.type,
                               AutocompleteMatchType::NUM_TYPES);
     if (profile_->GetNetworkPredictor()) {
       profile_->GetNetworkPredictor()->AnticipateOmniboxUrl(
           match.destination_url,
           predictors::AutocompleteActionPredictor::IsPreconnectable(match));
     }
     // We could prefetch the alternate nav URL, if any, but because there
     // can be many of these as a user types an initial series of characters,
     // the OS DNS cache could suffer eviction problems for minimal gain.
   }
 }