NoStatePrefetch: Remove kNoStatePrefetchFeature flag

This flag is now enabled by default and no longer necessary, so this CL
removes it.

We could remove more code (e.g., PrerenderManager::SetMode()), but this
CL focuses on the flag to minimize changes. Subsequent CLs will remove
them.

Bug: 632361
Change-Id: Ib4a0edfbfb4c62c6e98a112ecf7fdfa604063454
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2485412
Commit-Queue: Hiroki Nakagawa <nhiroki@chromium.org>
Reviewed-by: Robert Ogden <robertogden@chromium.org>
Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Reviewed-by: Angela Yoeurng <yoangela@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#818823}

chrome/browser/chrome_browser_field_trials_desktop.cc

@@ -14,7 +14,6 @@
 #include "chrome/common/chrome_paths.h"
 #include "chrome/common/chrome_switches.h"
 #include "components/metrics/persistent_system_profile.h"
-#include "components/prerender/browser/prerender_field_trial.h"
 #include "components/variations/variations_associated_data.h"
 #include "content/public/common/content_switches.h"
 
@@ -44,7 +43,6 @@ void SetupStunProbeTrial() {
 }  // namespace
 
 void SetupDesktopFieldTrials() {
-  prerender::ConfigureNoStatePrefetch();
   SetupStunProbeTrial();
 }
 

chrome/browser/chrome_browser_field_trials_mobile.cc

@@ -4,20 +4,12 @@
 
 #include "chrome/browser/chrome_browser_field_trials_mobile.h"
 
-#include "build/build_config.h"
 #include "chrome/browser/browser_process.h"
 
-#if defined(OS_ANDROID)
-#include "components/prerender/browser/prerender_field_trial.h"
-#endif
-
 namespace chrome {
 
 void SetupMobileFieldTrials() {
   DCHECK(!g_browser_process);
-#if defined(OS_ANDROID)
-  prerender::ConfigureNoStatePrefetch();
-#endif
 }
 
 }  // namespace chrome

chrome/browser/predictors/autocomplete_action_predictor.cc

@@ -27,7 +27,6 @@
 #include "components/omnibox/browser/autocomplete_result.h"
 #include "components/omnibox/browser/omnibox_log.h"
 #include "components/omnibox/browser/omnibox_popup_model.h"
-#include "components/prerender/browser/prerender_field_trial.h"
 #include "components/prerender/browser/prerender_handle.h"
 #include "components/prerender/browser/prerender_manager.h"
 #include "content/public/browser/browser_thread.h"
@@ -204,13 +203,9 @@ AutocompleteActionPredictor::Action
     }
   }
 
-  // Downgrade prerender to preconnect if this is a search match or if
-  // nostate-prefetch is disabled.
-  if (action == ACTION_PRERENDER &&
-      (AutocompleteMatch::IsSearchType(match.type) ||
-       !prerender::IsNoStatePrefetchEnabled())) {
+  // Downgrade prerender to preconnect if this is a search match.
+  if (action == ACTION_PRERENDER && AutocompleteMatch::IsSearchType(match.type))
     action = ACTION_PRECONNECT;
-  }
 
   return action;
 }

chrome/browser/prerender/prerender_unittest.cc

@@ -483,8 +483,6 @@ class PrerenderTest : public testing::Test {
 
 TEST_F(PrerenderTest, RespectsThirdPartyCookiesPref) {
   GURL url("http://www.google.com/");
-  ASSERT_TRUE(IsNoStatePrefetchEnabled());
-
   profile()->GetPrefs()->SetInteger(
       prefs::kCookieControlsMode,
       static_cast<int>(content_settings::CookieControlsMode::kBlockThirdParty));
@@ -651,7 +649,6 @@ TEST_F(PrerenderTest, PredictorPrefetchHoldbackOffPredictorReferrer) {
 // Flaky on Android and Mac, crbug.com/1087876.
 TEST_F(PrerenderTest, DISABLED_PrerenderDisabledOnLowEndDevice) {
   GURL url("http://www.google.com/");
-  ASSERT_TRUE(IsNoStatePrefetchEnabled());
   prerender_manager()->SetIsLowEndDevice(true);
   EXPECT_FALSE(AddSimplePrerender(url));
   histogram_tester().ExpectUniqueSample("Prerender.FinalStatus",
@@ -983,7 +980,6 @@ TEST_F(PrerenderTest, MaxConcurrencyTest) {
 
 // Flaky on Android: https://crbug.com/1105908
 TEST_F(PrerenderTest, DISABLED_AliasURLTest) {
-  ASSERT_TRUE(IsNoStatePrefetchEnabled());
   SetConcurrency(7);
 
   GURL url("http://www.google.com/");

chrome/browser/ui/omnibox/chrome_omnibox_client.cc

@@ -51,7 +51,6 @@
 #include "components/omnibox/browser/omnibox_controller_emitter.h"
 #include "components/omnibox/browser/search_provider.h"
 #include "components/omnibox/common/omnibox_features.h"
-#include "components/prerender/browser/prerender_field_trial.h"
 #include "components/search_engines/template_url_service.h"
 #include "components/sessions/content/session_tab_helper.h"
 #include "components/translate/core/browser/translate_manager.h"
@@ -311,12 +310,6 @@ gfx::Image ChromeOmniboxClient::GetFaviconForKeywordSearchProvider(
                                              std::move(on_favicon_fetched));
 }
 
-void ChromeOmniboxClient::OnCurrentMatchChanged(
-    const AutocompleteMatch& match) {
-  if (!prerender::IsNoStatePrefetchEnabled())
-    DoPreconnect(match);
-}
-
 void ChromeOmniboxClient::OnTextChanged(const AutocompleteMatch& current_match,
                                         bool user_input_in_progress,
                                         const base::string16& user_text,

chrome/browser/ui/omnibox/chrome_omnibox_client.h

@@ -71,7 +71,6 @@ class ChromeOmniboxClient : public OmniboxClient {
   gfx::Image GetFaviconForKeywordSearchProvider(
       const TemplateURL* template_url,
       FaviconFetchedCallback on_favicon_fetched) override;
-  void OnCurrentMatchChanged(const AutocompleteMatch& match) override;
   void OnTextChanged(const AutocompleteMatch& current_match,
                      bool user_input_in_progress,
                      const base::string16& user_text,

components/omnibox/browser/omnibox_client.h

@@ -137,9 +137,6 @@ class OmniboxClient {
       const TemplateURL* template_url,
       FaviconFetchedCallback on_favicon_fetched);
 
-  // Called when the current autocomplete match has changed.
-  virtual void OnCurrentMatchChanged(const AutocompleteMatch& match) {}
-
   // Called when the text may have changed in the edit.
   virtual void OnTextChanged(const AutocompleteMatch& current_match,
                              bool user_input_in_progress,

components/omnibox/browser/omnibox_edit_model.cc

@@ -1539,8 +1539,6 @@ void OmniboxEditModel::OnCurrentMatchChanged() {
 
   const AutocompleteMatch& match = omnibox_controller_->current_match();
 
-  client_->OnCurrentMatchChanged(match);
-
   // We store |keyword| and |is_keyword_hint| in temporary variables since
   // OnPopupDataChanged use their previous state to detect changes.
   base::string16 keyword;

components/prerender/browser/prerender_field_trial.cc

@@ -11,25 +11,10 @@
 
 namespace prerender {
 
-const base::Feature kNoStatePrefetchFeature{"NoStatePrefetch",
-                                            base::FEATURE_ENABLED_BY_DEFAULT};
-
 const base::Feature kGWSPrefetchHoldback{"GWSPrefetchHoldback",
                                          base::FEATURE_DISABLED_BY_DEFAULT};
 
 const base::Feature kNavigationPredictorPrefetchHoldback{
     "NavigationPredictorPrefetchHoldback", base::FEATURE_DISABLED_BY_DEFAULT};
 
-void ConfigureNoStatePrefetch() {
-  auto mode = PrerenderManager::PRERENDER_MODE_NOSTATE_PREFETCH;
-  if (!base::FeatureList::IsEnabled(kNoStatePrefetchFeature))
-    mode = PrerenderManager::PRERENDER_MODE_SIMPLE_LOAD_EXPERIMENT;
-  PrerenderManager::SetMode(mode);
-}
-
-bool IsNoStatePrefetchEnabled() {
-  return PrerenderManager::GetMode() ==
-         PrerenderManager::PRERENDER_MODE_NOSTATE_PREFETCH;
-}
-
 }  // namespace prerender

components/prerender/browser/prerender_field_trial.h

@@ -9,20 +9,12 @@
 
 namespace prerender {
 
-// These Finch feature and parameter strings exposed for for testing.
-extern const base::Feature kNoStatePrefetchFeature;
-
 // Preconnects instead of prefetching from GWS.
 extern const base::Feature kGWSPrefetchHoldback;
 
 // Preconnects instead of prefetching from NavigationPredictor.
 extern const base::Feature kNavigationPredictorPrefetchHoldback;
 
-// Configures global state using kNoStatePrefetchFeature.
-void ConfigureNoStatePrefetch();
-
-bool IsNoStatePrefetchEnabled();
-
 }  // namespace prerender
 
 #endif  // COMPONENTS_PRERENDER_BROWSER_PRERENDER_FIELD_TRIAL_H_

components/prerender/browser/prerender_manager.cc

@@ -221,8 +221,6 @@ PrerenderManager::AddPrerenderFromNavigationPredictor(
     const GURL& url,
     SessionStorageNamespace* session_storage_namespace,
     const gfx::Size& size) {
-  DCHECK(IsNoStatePrefetchEnabled());
-
   return AddPrerenderWithPreconnectFallback(
       ORIGIN_NAVIGATION_PREDICTOR, url, content::Referrer(), base::nullopt,
       gfx::Rect(size), session_storage_namespace);
@@ -232,8 +230,6 @@ std::unique_ptr<PrerenderHandle> PrerenderManager::AddIsolatedPrerender(
     const GURL& url,
     SessionStorageNamespace* session_storage_namespace,
     const gfx::Size& size) {
-  DCHECK(IsNoStatePrefetchEnabled());
-
   // The preconnect fallback won't happen.
   return AddPrerenderWithPreconnectFallback(
       ORIGIN_ISOLATED_PRERENDER, url, content::Referrer(), base::nullopt,
@@ -579,7 +575,6 @@ PrerenderManager::AddPrerenderWithPreconnectFallback(
     return base::WrapUnique(new PrerenderHandle(preexisting_prerender_data));
   }
 
-  if (IsNoStatePrefetchEnabled()) {
   base::TimeDelta prefetch_age;
   GetPrefetchInformation(url, &prefetch_age, nullptr /* final_status*/,
                          nullptr /* origin */);
@@ -590,7 +585,6 @@ PrerenderManager::AddPrerenderWithPreconnectFallback(
                                             FINAL_STATUS_DUPLICATE);
     return nullptr;
   }
-  }
 
   // Do not prerender if there are too many render processes, and we would
   // have to use an existing one.  We do not want prerendering to happen in
@@ -658,10 +652,8 @@ PrerenderManager::AddPrerenderWithPreconnectFallback(
       CreatePrerenderContents(url, referrer, initiator_origin, origin);
   DCHECK(prerender_contents);
   PrerenderContents* prerender_contents_ptr = prerender_contents.get();
-  if (IsNoStatePrefetchEnabled()) {
   prerender_contents_ptr->SetPrerenderMode(
       prerender::mojom::PrerenderMode::kPrefetchOnly);
-  }
   active_prerenders_.push_back(
       std::make_unique<PrerenderData>(this, std::move(prerender_contents),
                                       GetExpiryTimeForNewPrerender(origin)));
@@ -992,8 +984,6 @@ void PrerenderManager::SkipPrerenderContentsAndMaybePreconnect(
 
 void PrerenderManager::RecordNetworkBytesConsumed(Origin origin,
                                                   int64_t prerender_bytes) {
-  if (!IsNoStatePrefetchEnabled())
-    return;
   int64_t recent_browser_context_bytes =
       browser_context_network_bytes_ -
       last_recorded_browser_context_network_bytes_;