[ios] Remove feature flag kEnableUnrealizedWebStates

The support for unrealized WebStates has been shipped to 100%.
Remove the feature flag kEnableUnrealizedWebStates that used to
control whether the feature is enabled or not.

Fixed: 1264453
Change-Id: I3b5ff05fa30c6961d207a330973bdaad435dec66
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3776541
Reviewed-by: Justin Cohen <justincohen@chromium.org>
Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1026217}

docs/ios/unrealized_web_state.md

@@ -1,6 +1,6 @@
 # Unrealized `WebState`
 
-> **Status**: implementation in progress.
+> **Status**: launched.
 
 On iOS, each tab is implemented by a `WebState` and some TabHelpers. As users
 can have many tabs open at the same time, but only few of them visible, an

ios/chrome/browser/flags/about_flags.mm

@@ -835,11 +835,6 @@ const flags_ui::FeatureEntry kFeatureEntries[] = {
     {"remove-extra-ntps", flag_descriptions::kRemoveExcessNTPsExperimentName,
      flag_descriptions::kRemoveExcessNTPsExperimentDescription,
      flags_ui::kOsIos, FEATURE_VALUE_TYPE(kRemoveExcessNTPs)},
-    {"lazily-create-web-state-on-restoration",
-     flag_descriptions::kLazilyCreateWebStateOnRestorationName,
-     flag_descriptions::kLazilyCreateWebStateOnRestorationDescription,
-     flags_ui::kOsIos,
-     FEATURE_VALUE_TYPE(web::features::kEnableUnrealizedWebStates)},
     {"enable-shortened-password-auto-fill-instruction",
      flag_descriptions::kEnableShortenedPasswordAutoFillInstructionName,
      flag_descriptions::kEnableShortenedPasswordAutoFillInstructionDescription,

ios/chrome/browser/flags/ios_chrome_flag_descriptions.cc

@@ -419,10 +419,6 @@ const char kIOSSharedHighlightingV2Description[] =
     "Enables improvements to text fragments UI, including a menu for removing "
     "or resharing a highlight.";
 
-const char kLazilyCreateWebStateOnRestorationName[] = "Unrealized WebStates";
-const char kLazilyCreateWebStateOnRestorationDescription[] =
-    "Create WebState in unrealized state upon session restoration.";
-
 const char kLeakDetectionUnauthenticatedName[] =
     "Leak detection for signed out users";
 const char kLeakDetectionUnauthenticatedDescription[] =

ios/chrome/browser/flags/ios_chrome_flag_descriptions.h

@@ -372,10 +372,6 @@ extern const char kIOSSharedHighlightingAmpDescription[];
 extern const char kIOSSharedHighlightingV2Name[];
 extern const char kIOSSharedHighlightingV2Description[];
 
-// Title and description for the flag to enable unrealized WebStates.
-extern const char kLazilyCreateWebStateOnRestorationName[];
-extern const char kLazilyCreateWebStateOnRestorationDescription[];
-
 // Title and description for the flag to enable leak detection for signed out
 // users.
 extern const char kLeakDetectionUnauthenticatedName[];

ios/web/common/features.h

@@ -56,10 +56,6 @@ extern const base::Feature kIOSSharedHighlightingColorChange;
 // interaction state.
 extern const base::Feature kSynthesizedRestoreSession;
 
-// Enable support for unrealized WebState upon session restoration.
-// See //docs/ios/unrealized_web_state.md for more information.
-extern const base::Feature kEnableUnrealizedWebStates;
-
 // Enables user control for camera and/or microphone access for a specific site
 // through site settings during its lifespan. When enabled, each web state will
 // keep track of whether camera and/or microphone access is granted by the user

ios/web/common/features.mm

@@ -49,9 +49,6 @@ const base::Feature kIOSSharedHighlightingColorChange{
 const base::Feature kSynthesizedRestoreSession{
     "SynthesizedRestoreSession", base::FEATURE_ENABLED_BY_DEFAULT};
 
-const base::Feature kEnableUnrealizedWebStates{
-    "EnableUnrealizedWebStates", base::FEATURE_ENABLED_BY_DEFAULT};
-
 const base::Feature kMediaPermissionsControl{"MediaPermissionsControl",
                                              base::FEATURE_ENABLED_BY_DEFAULT};
 

ios/web/web_state/web_state_impl.mm

@@ -28,10 +28,10 @@
 namespace web {
 namespace {
 
-// With |kEnableUnrealizedWebStates|, detect inefficient usage of WebState
+// Detect inefficient usage of WebState realization. Various bugs have
-// realization. Various bugs have triggered the realization of the entire
+// triggered the realization of the entire WebStateList. Detect this by
-// WebStateList. Detect this by checking for the realization of 3 WebStates
+// checking for the realization of 3 WebStates within one second. Only
-// within one second. Only report this error once per launch.
+// report this error once per launch.
 constexpr size_t kMaxEvents = 3;
 constexpr CFTimeInterval kWindowSizeInSeconds = 1.0f;
 size_t g_last_realized_count = 0;
@@ -82,8 +82,7 @@ WebStateImpl::WebStateImpl(const CreateParams& params)
 
 WebStateImpl::WebStateImpl(const CreateParams& params,
                            CRWSessionStorage* session_storage) {
-  if (session_storage &&
+  if (session_storage) {
-      base::FeatureList::IsEnabled(features::kEnableUnrealizedWebStates)) {
     saved_ = std::make_unique<SerializedData>(this, params, session_storage);
   } else {
     pimpl_ = std::make_unique<RealizedWebState>(this);