Remove NavigationPredictor Renderer Warmup Code

This experiment never worked out and the experiment has been disabled.
This CL removes all related code.

Note that PrefetchProxy spare renderer is implemented within the
PrefetchProxy code, not here. Omnibox spare renderer is also unrelated
to this code.

Bug: 1115259
Change-Id: I8631bd1d2292a4c0d2a1a190b9b6563c4012b97a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2723694
Commit-Queue: Robert Ogden <robertogden@chromium.org>
Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#859069}

chrome/browser/BUILD.gn

@@ -851,8 +851,6 @@ static_library("browser") {
     "navigation_predictor/navigation_predictor_keyed_service_factory.h",
     "navigation_predictor/navigation_predictor_preconnect_client.cc",
     "navigation_predictor/navigation_predictor_preconnect_client.h",
-    "navigation_predictor/navigation_predictor_renderer_warmup_client.cc",
-    "navigation_predictor/navigation_predictor_renderer_warmup_client.h",
     "navigation_predictor/search_engine_preconnector.cc",
     "navigation_predictor/search_engine_preconnector.h",
     "net/chrome_mojo_proxy_resolver_factory.cc",

chrome/browser/about_flags.cc

@@ -3457,10 +3457,6 @@ const FeatureEntry kFeatureEntries[] = {
      flag_descriptions::kEnableNavigationPredictorDescription,
      kOsCrOS | kOsLinux,
      FEATURE_VALUE_TYPE(blink::features::kNavigationPredictor)},
-    {"enable-navigation-predictor-renderer-warmup",
-     flag_descriptions::kEnableNavigationPredictorRendererWarmupName,
-     flag_descriptions::kEnableNavigationPredictorRendererWarmupDescription,
-     kOsAll, FEATURE_VALUE_TYPE(features::kNavigationPredictorRendererWarmup)},
 #endif  // BUILDFLAG(IS_CHROMEOS_ASH) || OS_LINUX
     {"enable-preconnect-to-search",
      flag_descriptions::kEnablePreconnectToSearchName,

chrome/browser/flag-metadata.json

@@ -2064,11 +2064,6 @@
     "owners": [ "tbansal", "ryansturm", "instant-nav" ],
     "expiry_milestone": 90
   },
-  {
-    "name": "enable-navigation-predictor-renderer-warmup",
-    "owners": [ "tbansal", "ryansturm", "instant-nav" ],
-    "expiry_milestone": 95
-  },
   {
     "name": "enable-network-logging-to-file",
     "owners": [ "net-dev" ],

chrome/browser/flag_descriptions.cc

@@ -640,12 +640,6 @@ const char kEnableNavigationPredictorDescription[] =
     "Enables navigation predictor feature that predicts the next likely "
     "navigation using a set of heuristics.";
 
-const char kEnableNavigationPredictorRendererWarmupName[] =
-    "Enables navigation predictor";
-const char kEnableNavigationPredictorRendererWarmupDescription[] =
-    "Enables navigation predictor feature that predicts the next likely "
-    "navigation using a set of heuristics.";
-
 const char kEnablePreconnectToSearchName[] =
     "Enables preconnections to default search engine";
 const char kEnablePreconnectToSearchDescription[] =

chrome/browser/flag_descriptions.h

@@ -400,9 +400,6 @@ extern const char kEnableSaveDataDescription[];
 extern const char kEnableNavigationPredictorName[];
 extern const char kEnableNavigationPredictorDescription[];
 
-extern const char kEnableNavigationPredictorRendererWarmupName[];
-extern const char kEnableNavigationPredictorRendererWarmupDescription[];
-
 extern const char kEnablePreconnectToSearchName[];
 extern const char kEnablePreconnectToSearchDescription[];
 

chrome/browser/navigation_predictor/navigation_predictor_features.cc

@@ -24,7 +24,4 @@ const base::Feature
         "NavigationPredictorEnablePreconnectOnSameDocumentNavigations",
         base::FEATURE_DISABLED_BY_DEFAULT};
 
-const base::Feature kNavigationPredictorRendererWarmup{
-    "NavigationPredictorRendererWarmup", base::FEATURE_DISABLED_BY_DEFAULT};
-
 }  // namespace features

chrome/browser/navigation_predictor/navigation_predictor_features.h

@@ -14,7 +14,6 @@ namespace features {
 extern const base::Feature kNavigationPredictorPreconnectHoldback;
 extern const base::Feature
     kNavigationPredictorEnablePreconnectOnSameDocumentNavigations;
-extern const base::Feature kNavigationPredictorRendererWarmup;
 
 }  // namespace features
 

chrome/browser/navigation_predictor/navigation_predictor_keyed_service.cc

@@ -12,7 +12,6 @@
 #include "base/time/default_tick_clock.h"
 #include "base/values.h"
 #include "build/build_config.h"
-#include "chrome/browser/navigation_predictor/navigation_predictor_renderer_warmup_client.h"
 #include "chrome/browser/profiles/profile.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/browser_thread.h"
@@ -160,9 +159,7 @@ NavigationPredictorKeyedService::Prediction::web_contents() const {
 NavigationPredictorKeyedService::NavigationPredictorKeyedService(
     content::BrowserContext* browser_context)
     : search_engine_preconnector_(browser_context),
-      renderer_warmup_client_(
-          std::make_unique<NavigationPredictorRendererWarmupClient>(
-              Profile::FromBrowserContext(browser_context))),
+
       tick_clock_(base::DefaultTickClock::GetInstance()) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   DCHECK(!browser_context->IsOffTheRecord());
@@ -171,8 +168,6 @@ NavigationPredictorKeyedService::NavigationPredictorKeyedService(
   // Start preconnecting to the search engine.
   search_engine_preconnector_.StartPreconnecting(/*with_startup_delay=*/true);
 #endif
-
-  AddObserver(renderer_warmup_client_.get());
 }
 
 NavigationPredictorKeyedService::~NavigationPredictorKeyedService() {

chrome/browser/navigation_predictor/navigation_predictor_keyed_service.h

@@ -21,8 +21,6 @@ class BrowserContext;
 class WebContents;
 }  // namespace content
 
-class NavigationPredictorRendererWarmupClient;
-
 // Keyed service that can be used to receive notifications about the URLs for
 // the next predicted navigation.
 class NavigationPredictorKeyedService : public KeyedService {
@@ -166,10 +164,6 @@ class NavigationPredictorKeyedService : public KeyedService {
   // Manages preconnecting to the user's default search engine.
   SearchEnginePreconnector search_engine_preconnector_;
 
-  // Manages warming up a spare renderer based on predictions.
-  std::unique_ptr<NavigationPredictorRendererWarmupClient>
-      renderer_warmup_client_;
-
   std::unordered_set<content::WebContents*> visible_web_contents_;
 
   base::TimeTicks last_web_contents_state_change_time_;