Revert "[ios] Remove Unused FullScreen Feature Flags"

This reverts commit 9384d0a2.

Reason for revert: <INSERT REASONING HERE>

Original change's description:
> [ios] Remove Unused FullScreen Feature Flags
> 
> There is no need for ViewportAdjustmentExperiment since the only experiment
> remaining is just the kSmoothScrollingDefault feature flag.
> GetActiveViewportExperiment() can just be a function that returns
> whether or not smooth scrolling is turned on. GetActiveViewportExperiment()
> and ViewportAdjustmentExperiment are still needed for downstream compatibility,
> and will be removed in a subsequent CL.
> 
> Bug: 914042
> Change-Id: I57bcd13dafaafb3b3a05ec65f23dacf2936e81e9
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1799663
> Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
> Commit-Queue: Chris Lu <thegreenfrog@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#697673}

TBR=kkhorimoto@chromium.org,thegreenfrog@chromium.org

Change-Id: Id1e0df1c06297d0249717102d5dc87e6343b6b63
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 914042
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1812091Reviewed-by: Chris Lu <thegreenfrog@chromium.org>
Commit-Queue: Chris Lu <thegreenfrog@chromium.org>
Cr-Commit-Position: refs/heads/master@{#697840}

ios/chrome/browser/flags/about_flags.mm

@@ -326,9 +326,11 @@ const flags_ui::FeatureEntry kFeatureEntries[] = {
      flags_ui::kOsIos,
      FEATURE_VALUE_TYPE(autofill::features::kAutofillRichMetadataQueries)},
     {"fullscreen-viewport-adjustment-experiment",
-     flag_descriptions::kFullscreenSmoothScrollingName,
-     flag_descriptions::kFullscreenSmoothScrollingDescription, flags_ui::kOsIos,
-     FEATURE_VALUE_TYPE(fullscreen::features::kSmoothScrollingDefault)},
+     flag_descriptions::kFullscreenViewportAdjustmentExperimentName,
+     flag_descriptions::kFullscreenViewportAdjustmentExperimentDescription,
+     flags_ui::kOsIos,
+     MULTI_VALUE_TYPE(
+         fullscreen::features::kViewportAdjustmentExperimentChoices)},
     {"autofill-enforce-min-required-fields-for-heuristics",
      flag_descriptions::kAutofillEnforceMinRequiredFieldsForHeuristicsName,
      flag_descriptions::
@@ -507,6 +509,9 @@ const flags_ui::FeatureEntry kFeatureEntries[] = {
     {"language-settings", flag_descriptions::kLanguageSettingsName,
      flag_descriptions::kLanguageSettingsDescription, flags_ui::kOsIos,
      FEATURE_VALUE_TYPE(kLanguageSettings)},
+    {"lock-bottom-toolbar", flag_descriptions::kLockBottomToolbarName,
+     flag_descriptions::kLockBottomToolbarDescription, flags_ui::kOsIos,
+     FEATURE_VALUE_TYPE(fullscreen::features::kLockBottomToolbar)},
     {"toolbar-new-tab-button", flag_descriptions::kToolbarNewTabButtonName,
      flag_descriptions::kToolbarNewTabButtonDescription, flags_ui::kOsIos,
      FEATURE_VALUE_TYPE(kToolbarNewTabButton)},

ios/chrome/browser/flags/ios_chrome_flag_descriptions.cc

@@ -204,11 +204,11 @@ const char kFindInPageiFrameName[] = "Find in Page in iFrames.";
 const char kFindInPageiFrameDescription[] =
     "When enabled, Find In Page will search in iFrames.";
 
-const char kFullscreenSmoothScrollingName[] = "Fullscreen Smooth Scrolling";
-const char kFullscreenSmoothScrollingDescription[] =
-    "When enabled, the web view's insets are updated for scoll events. If "
-    "disabled, the "
-    "the web view's frame are updated.";
+const char kFullscreenViewportAdjustmentExperimentName[] =
+    "Fullscreen Viewport Adjustment Mode";
+const char kFullscreenViewportAdjustmentExperimentDescription[] =
+    "The different ways in which the web view's viewport is updated for scroll "
+    "events.  The default option updates the web view's frame.";
 
 const char kIgnoresViewportScaleLimitsName[] = "Ignore Viewport Scale Limits";
 const char kIgnoresViewportScaleLimitsDescription[] =
@@ -230,6 +230,11 @@ const char kLanguageSettingsDescription[] =
     "Enables the Language Settings page allowing modifications to user "
     "preferred languages and translate preferences.";
 
+const char kLockBottomToolbarName[] = "Lock bottom toolbar";
+const char kLockBottomToolbarDescription[] =
+    "When enabled, the bottom toolbar will not get collapsed when scrolling "
+    "into fullscreen mode.";
+
 const char kMarkHttpAsName[] = "Mark non-secure origins as non-secure";
 const char kMarkHttpAsDescription[] = "Change the UI treatment for HTTP pages";
 

ios/chrome/browser/flags/ios_chrome_flag_descriptions.h

@@ -167,10 +167,10 @@ extern const char kFillOnAccountSelectHttpDescription[];
 extern const char kFindInPageiFrameName[];
 extern const char kFindInPageiFrameDescription[];
 
-// Title and description for the flag to update the web view's insets for scroll
-// events.
-extern const char kFullscreenSmoothScrollingName[];
-extern const char kFullscreenSmoothScrollingDescription[];
+// Title and description for the command line switch used to determine the
+// active fullscreen viewport adjustment mode.
+extern const char kFullscreenViewportAdjustmentExperimentName[];
+extern const char kFullscreenViewportAdjustmentExperimentDescription[];
 
 // Title and description for the flag to ignore viewport scale limits.
 extern const char kIgnoresViewportScaleLimitsName[];
@@ -189,6 +189,10 @@ extern const char kInProductHelpDemoModeDescription[];
 extern const char kLanguageSettingsName[];
 extern const char kLanguageSettingsDescription[];
 
+// Title and description for the flag to lock the bottom toolbar into place.
+extern const char kLockBottomToolbarName[];
+extern const char kLockBottomToolbarDescription[];
+
 // Title, description, and options for the MarkHttpAs setting that controls
 // display of omnibox warnings about non-secure pages.
 extern const char kMarkHttpAsName[];

ios/chrome/browser/ui/browser_view/browser_view_controller.mm

@@ -597,6 +597,9 @@ NSString* const kBrowserViewControllerSnackbarCategory =
 // The webState of the active tab.
 @property(nonatomic, readonly) web::WebState* currentWebState;
 
+// Whether the safe area insets should be used to adjust the viewport.
+@property(nonatomic, readonly) BOOL usesSafeInsetsForViewportAdjustments;
+
 // Whether the keyboard observer helper is viewed
 @property(nonatomic, strong) KeyboardObserverHelper* observer;
 
@@ -1069,6 +1072,15 @@ NSString* const kBrowserViewControllerSnackbarCategory =
              : nullptr;
 }
 
+- (BOOL)usesSafeInsetsForViewportAdjustments {
+  fullscreen::features::ViewportAdjustmentExperiment viewportExperiment =
+      fullscreen::features::GetActiveViewportExperiment();
+  return viewportExperiment ==
+             fullscreen::features::ViewportAdjustmentExperiment::SAFE_AREA ||
+         viewportExperiment ==
+             fullscreen::features::ViewportAdjustmentExperiment::HYBRID;
+}
+
 - (BubblePresenter*)bubblePresenter {
   if (!_bubblePresenter && self.browserState) {
     self.bubblePresenter =
@@ -1674,7 +1686,7 @@ NSString* const kBrowserViewControllerSnackbarCategory =
   self.secondaryToolbarNoFullscreenHeightConstraint.constant =
       [self secondaryToolbarHeightWithInset];
   [self updateFootersForFullscreenProgress:self.footerFullscreenProgress];
-  if (self.currentWebState) {
+  if (!self.usesSafeInsetsForViewportAdjustments && self.currentWebState) {
     UIEdgeInsets contentPadding =
         self.currentWebState->GetWebViewProxy().contentInset;
     contentPadding.bottom = AlignValueToPixel(
@@ -3816,6 +3828,9 @@ NSString* const kBrowserViewControllerSnackbarCategory =
 // Translates the footer view up and down according to |progress|, where a
 // progress of 1.0 fully shows the footer and a progress of 0.0 fully hides it.
 - (void)updateFootersForFullscreenProgress:(CGFloat)progress {
+  // If the bottom toolbar is locked into place, reset |progress| to 1.0.
+  if (base::FeatureList::IsEnabled(fullscreen::features::kLockBottomToolbar))
+    progress = 1.0;
 
   self.footerFullscreenProgress = progress;
 
@@ -3858,10 +3873,26 @@ NSString* const kBrowserViewControllerSnackbarCategory =
   // safe area, so the unsafe top height must be added.
   CGFloat top = AlignValueToPixel(
       self.headerHeight + (progress - 1.0) * [self primaryToolbarHeightDelta]);
-  CGFloat bottom =
-      AlignValueToPixel(progress * [self secondaryToolbarHeightWithInset]);
+  // If the bottom toolbar is locked into place, use 1.0 instead of |progress|.
+  CGFloat bottomProgress =
+      base::FeatureList::IsEnabled(fullscreen::features::kLockBottomToolbar)
+          ? 1.0
+          : progress;
+  CGFloat bottom = AlignValueToPixel(bottomProgress *
+                                     [self secondaryToolbarHeightWithInset]);
+
+  if (self.usesSafeInsetsForViewportAdjustments) {
+    if (fullscreen::features::GetActiveViewportExperiment() ==
+        fullscreen::features::ViewportAdjustmentExperiment::HYBRID) {
+      [self updateWebViewFrameForBottomOffset:bottom];
+    }
 
-  [self updateContentPaddingForTopToolbarHeight:top bottomToolbarHeight:bottom];
+    [self updateBrowserSafeAreaForTopToolbarHeight:top
+                               bottomToolbarHeight:bottom];
+  } else {
+    [self updateContentPaddingForTopToolbarHeight:top
+                              bottomToolbarHeight:bottom];
+  }
 }
 
 // Updates the frame of the web view so that it's |offset| from the bottom of

ios/chrome/browser/ui/fullscreen/fullscreen_features.h

@@ -11,25 +11,35 @@
 namespace fullscreen {
 namespace features {
 
-// Feature used by finch config to enable smooth scrolling when the default
-// viewport adjustment experiment is selected via command line switches.
-extern const base::Feature kSmoothScrollingDefault;
+// The name of the command line switch used to control the method by which the
+// viewport of the content area is updated by scrolling events.
+extern const char kViewportAdjustmentExperimentCommandLineSwitch[];
+
+// The available viewport adjustment experiments.  The choices in this array
+// correspond with the ViewportAdjustmentExperiment values.
+extern const flags_ui::FeatureEntry::Choice
+    kViewportAdjustmentExperimentChoices[6];
 
 // Enum type describing viewport adjustment experiments.
 enum class ViewportAdjustmentExperiment : short {
   FRAME = 0,      // Adjust the viewport by resizing the entire WKWebView.
+  CONTENT_INSET,  // Adjust the viewport by updating the WKWebView's scroll view
+                  // contentInset.
+  SAFE_AREA,  // Adjust the viewport by updating the safe area of the browser
+              // container view.
+  HYBRID,  // Translates the web view up and down and updates the viewport using
+           // safe area insets.
   SMOOTH_SCROLLING,  // Adjusts the viewport using the smooth scrolling
                      // workaround.
 };
 
 // Convenience method for retrieving the active viewport adjustment experiment
-// from the command line. TODO(crbug.com/914042): Remove once the internal
-// references are moved to ShouldUseSmoothScrolling().
+// from the command line.
 ViewportAdjustmentExperiment GetActiveViewportExperiment();
 
-// Convenience method for determining when to adjust the viewport by resizing
-// WKWebView or using smooth scrolling.
-bool ShouldUseSmoothScrolling();
+// Used to control whether the bottom toolbar should be locked into the extended
+// position (i.e. fullscreen progress == 1.0).
+extern const base::Feature kLockBottomToolbar;
 
 }  // namespace features
 }  // namespace fullscreen

ios/chrome/browser/ui/fullscreen/fullscreen_features.mm

@@ -11,21 +11,63 @@
 #error "This file requires ARC support."
 #endif
 
-namespace fullscreen {
-namespace features {
+namespace {
+// The command line values for the content inset and safe area experiment
+// choices.
+const char kFrameChoiceValue[] = "frame";
+const char kContentInsetChoiceValue[] = "content-inset";
+const char kSafeAreaChoiceValue[] = "safe-area";
+const char kHybridChoiceValue[] = "hybrid";
+const char kSmoothScrollingChoiceValue[] = "smooth";
 
+// Feature used by finch config to enable smooth scrolling when the default
+// viewport adjustment experiment is selected via command line switches.
 const base::Feature kSmoothScrollingDefault{"FullscreenSmoothScrollingDefault",
                                             base::FEATURE_ENABLED_BY_DEFAULT};
+}
+
+namespace fullscreen {
+namespace features {
+
+const char kViewportAdjustmentExperimentCommandLineSwitch[] =
+    "fullscreen-viewport-adjustment-experiment";
+
+const flags_ui::FeatureEntry::Choice kViewportAdjustmentExperimentChoices[] = {
+    {flags_ui::kGenericExperimentChoiceDefault, "", ""},
+    {"Update Content Inset", kViewportAdjustmentExperimentCommandLineSwitch,
+     "content-inset"},
+    {"Update Safe Area", kViewportAdjustmentExperimentCommandLineSwitch,
+     "safe-area"},
+    {"Use Hybrid Implementation",
+     kViewportAdjustmentExperimentCommandLineSwitch, "hybrid"},
+    {"Use Smooth Scrolling", kViewportAdjustmentExperimentCommandLineSwitch,
+     "smooth"},
+    {"Update Frame", kViewportAdjustmentExperimentCommandLineSwitch, "frame"}};
 
 ViewportAdjustmentExperiment GetActiveViewportExperiment() {
-  return ShouldUseSmoothScrolling()
+  const base::CommandLine* command_line =
+      base::CommandLine::ForCurrentProcess();
+  if (command_line->HasSwitch(kViewportAdjustmentExperimentCommandLineSwitch)) {
+    std::string viewport_experiment = command_line->GetSwitchValueASCII(
+        kViewportAdjustmentExperimentCommandLineSwitch);
+    if (viewport_experiment == std::string(kContentInsetChoiceValue))
+      return ViewportAdjustmentExperiment::CONTENT_INSET;
+    if (viewport_experiment == std::string(kSafeAreaChoiceValue))
+      return ViewportAdjustmentExperiment::SAFE_AREA;
+    if (viewport_experiment == std::string(kHybridChoiceValue))
+      return ViewportAdjustmentExperiment::HYBRID;
+    if (viewport_experiment == std::string(kSmoothScrollingChoiceValue))
+      return ViewportAdjustmentExperiment::SMOOTH_SCROLLING;
+    if (viewport_experiment == std::string(kFrameChoiceValue))
+      return ViewportAdjustmentExperiment::FRAME;
+  }
+  return base::FeatureList::IsEnabled(kSmoothScrollingDefault)
              ? ViewportAdjustmentExperiment::SMOOTH_SCROLLING
              : ViewportAdjustmentExperiment::FRAME;
 }
 
-bool ShouldUseSmoothScrolling() {
-  return base::FeatureList::IsEnabled(kSmoothScrollingDefault);
-}
+const base::Feature kLockBottomToolbar{"LockBottomToolbar",
+                                       base::FEATURE_DISABLED_BY_DEFAULT};
 
 }  // namespace features
 }  // namespace fullscreen

ios/chrome/browser/ui/fullscreen/fullscreen_model.h

@@ -73,10 +73,14 @@ class FullscreenModel : public ChromeBroadcastObserverInterface {
 
   // Returns the toolbar insets at |progress|.
   UIEdgeInsets GetToolbarInsetsAtProgress(CGFloat progress) const {
+    const CGFloat kBottomToolbarProgress =
+        base::FeatureList::IsEnabled(fullscreen::features::kLockBottomToolbar)
+            ? 1.0
+            : progress;
     return UIEdgeInsetsMake(
         collapsed_toolbar_height_ +
             progress * (expanded_toolbar_height_ - collapsed_toolbar_height_),
-        0, progress * bottom_toolbar_height_, 0);
+        0, kBottomToolbarProgress * bottom_toolbar_height_, 0);
   }
 
   // Increments and decrements |disabled_counter_| for features that require the

ios/chrome/browser/ui/fullscreen/fullscreen_web_state_observer.mm

@@ -28,6 +28,8 @@
 #error "This file requires ARC support."
 #endif
 
+using fullscreen::features::ViewportAdjustmentExperiment;
+
 FullscreenWebStateObserver::FullscreenWebStateObserver(
     FullscreenController* controller,
     FullscreenModel* model,
@@ -81,13 +83,18 @@ void FullscreenWebStateObserver::DidFinishNavigation(
   // - For normal pages, using |contentInset| breaks the layout of fixed-
   //   position DOM elements, so top padding must be accomplished by updating
   //   the WKWebView's frame.
+  bool force_content_inset =
+      fullscreen::features::GetActiveViewportExperiment() ==
+      ViewportAdjustmentExperiment::CONTENT_INSET;
   bool is_pdf = web_state->GetContentsMimeType() == "application/pdf";
+  bool use_content_inset = force_content_inset || is_pdf;
   id<CRWWebViewProxy> web_view_proxy = web_state->GetWebViewProxy();
-  web_view_proxy.shouldUseViewContentInset = is_pdf;
+  web_view_proxy.shouldUseViewContentInset = use_content_inset;
 
-  model_->SetResizesScrollView(!is_pdf && !ios::GetChromeBrowserProvider()
-                                               ->GetFullscreenProvider()
-                                               ->IsInitialized());
+  model_->SetResizesScrollView(!use_content_inset &&
+                               !ios::GetChromeBrowserProvider()
+                                    ->GetFullscreenProvider()
+                                    ->IsInitialized());
 
   // Only reset the model for document-changing navigations or same-document
   // navigations that update the visible URL.

ios/chrome/browser/ui/overscroll_actions/overscroll_actions_controller.mm

@@ -32,6 +32,8 @@
 #error "This file requires ARC support."
 #endif
 
+using fullscreen::features::ViewportAdjustmentExperiment;
+
 namespace {
 // This enum is used to record the overscroll actions performed by the user on
 // the histogram named |OverscrollActions|.
@@ -569,9 +571,12 @@ NSString* const kOverscrollActionsDidEnd = @"OverscrollActionsDidStop";
 - (BOOL)viewportAdjustsContentInset {
   if (_webViewProxy.shouldUseViewContentInset)
     return YES;
-  return ios::GetChromeBrowserProvider()
-      ->GetFullscreenProvider()
-      ->IsInitialized();
+  ViewportAdjustmentExperiment experiment =
+      fullscreen::features::GetActiveViewportExperiment();
+  return experiment == ViewportAdjustmentExperiment::SMOOTH_SCROLLING &&
+         ios::GetChromeBrowserProvider()
+             ->GetFullscreenProvider()
+             ->IsInitialized();
 }
 
 - (void)recordMetricForTriggeredAction:(OverscrollAction)action {