[ios] Remove SnapshotDrawView experiment

This experiment could not be rolled out because it caused a flicker
in the UI.

Bug: 945811
Change-Id: I843bdf4666e0af17e31e9f27bb8aaf8433cb6274
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2765246
Auto-Submit: edchin <edchin@chromium.org>
Commit-Queue: Rohit Rao <rohitrao@chromium.org>
Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#863766}

ios/chrome/browser/flags/about_flags.mm

@@ -384,9 +384,6 @@
      flag_descriptions::kOmniboxLocalHistoryZeroSuggestName,
      flag_descriptions::kOmniboxLocalHistoryZeroSuggestDescription,
      flags_ui::kOsIos, FEATURE_VALUE_TYPE(omnibox::kLocalHistoryZeroSuggest)},
-    {"snapshot-draw-view", flag_descriptions::kSnapshotDrawViewName,
-     flag_descriptions::kSnapshotDrawViewDescription, flags_ui::kOsIos,
-     FEATURE_VALUE_TYPE(kSnapshotDrawView)},
 #if defined(DCHECK_IS_CONFIGURABLE)
     {"dcheck-is-fatal", flag_descriptions::kDcheckIsFatalName,
      flag_descriptions::kDcheckIsFatalDescription, flags_ui::kOsIos,

ios/chrome/browser/flags/ios_chrome_flag_descriptions.cc

@@ -406,10 +406,6 @@ const char kShowAutofillTypePredictionsDescription[] =
     "Annotates web forms with Autofill field type predictions as placeholder "
     "text.";
 
-const char kSnapshotDrawViewName[] = "Use DrawViewHierarchy for Snapshots";
-const char kSnapshotDrawViewDescription[] =
-    "When enabled, snapshots will be taken using |-drawViewHierarchy:|.";
-
 const char kSimplifySignOutIOSName[] = "Simplify sign-out";
 const char kSimplifySignOutIOSDescription[] =
     "When enabled, sign-out UI in the account table view is simplified.";

ios/chrome/browser/flags/ios_chrome_flag_descriptions.h

@@ -345,11 +345,6 @@ extern const char kShowAutofillTypePredictionsDescription[];
 extern const char kSimplifySignOutIOSName[];
 extern const char kSimplifySignOutIOSDescription[];
 
-// Title and description for the flag to use |-drawViewHierarchy:| for taking
-// snapshots.
-extern const char kSnapshotDrawViewName[];
-extern const char kSnapshotDrawViewDescription[];
-
 // Title and description for the flag to enable the Start Surface.
 extern const char kStartSurfaceName[];
 extern const char kStartSurfaceDescription[];

ios/chrome/browser/snapshots/snapshot_generator.mm

@@ -16,7 +16,6 @@
 #include "base/task/post_task.h"
 #import "ios/chrome/browser/snapshots/snapshot_cache.h"
 #import "ios/chrome/browser/snapshots/snapshot_generator_delegate.h"
-#include "ios/chrome/browser/ui/ui_feature_flags.h"
 #import "ios/chrome/browser/ui/util/uikit_ui_util.h"
 #include "ios/web/public/thread/web_task_traits.h"
 #include "ios/web/public/thread/web_thread.h"
@@ -215,24 +214,20 @@ - (UIImage*)snapshotBaseView:(UIView*)baseView
                         -frameInBaseView.origin.y);
   BOOL snapshotSuccess = YES;
 
-  // TODO(crbug.com/636188): |-drawViewHierarchyInRect:afterScreenUpdates:| is
-  // buggy on iOS 8/9/10 (and state is unknown for iOS 11) causing GPU glitches,
-  // screen redraws during animations, broken pinch to dismiss on tablet, etc.
-  // Ensure iOS 11 is not affected by these issues before turning on
-  // |kSnapshotDrawView| experiment. On the other hand, |-renderInContext:| is
-  // buggy for WKWebView, which is used for some Chromium pages such as "No
-  // internet" or "Site can't be reached".
-  BOOL useDrawViewHierarchy = ViewHierarchyContainsWKWebView(baseView) ||
-                              base::FeatureList::IsEnabled(kSnapshotDrawView);
   // |drawViewHierarchyInRect:| has undefined behavior when the view is not
   // in the visible view hierarchy. In practice, when this method is called
   // on a view that is part of view controller containment and not in the view
   // hierarchy, an UIViewControllerHierarchyInconsistency exception will be
   // thrown.
-  if (useDrawViewHierarchy && baseView.window) {
+  if (baseView.window && ViewHierarchyContainsWKWebView(baseView)) {
+    // TODO(crbug.com/636188): |-drawViewHierarchyInRect:afterScreenUpdates:| is
+    // buggy causing GPU glitches, screen redraws during animations, broken
+    // pinch to dismiss on tablet, etc.
     snapshotSuccess = [baseView drawViewHierarchyInRect:baseView.bounds
                                      afterScreenUpdates:YES];
   } else {
+    // |-renderInContext:| is buggy for WKWebView, which is used for some
+    // Chromium pages such as "No internet" or "Site can't be reached".
     [[baseView layer] renderInContext:context];
   }
   UIImage* image = nil;
@@ -293,16 +288,7 @@ - (void)drawOverlays:(NSArray<UIView*>*)overlays context:(CGContext*)context {
     // This shifts the context so that drawing starts at the overlay's offset.
     CGContextTranslateCTM(context, frameInWindow.origin.x,
                           frameInWindow.origin.y);
-    // |drawViewHierarchyInRect:| has undefined behavior when the view is not
-    // in the visible view hierarchy. In practice, when this method is called
-    // on a view that is part of view controller containment, an
-    // UIViewControllerHierarchyInconsistency exception will be thrown.
-    if (base::FeatureList::IsEnabled(kSnapshotDrawView) && overlay.window) {
-      // The rect's origin is ignored. Only size is used.
-      [overlay drawViewHierarchyInRect:overlay.bounds afterScreenUpdates:YES];
-    } else {
-      [[overlay layer] renderInContext:context];
-    }
+    [[overlay layer] renderInContext:context];
     CGContextRestoreGState(context);
   }
 }

ios/chrome/browser/ui/ui_feature_flags.cc

@@ -7,12 +7,6 @@
 const base::Feature kExpandedTabStrip{"ExpandedTabStrip",
                                       base::FEATURE_DISABLED_BY_DEFAULT};
 
-// TODO(crbug.com/945811): Using |-drawViewHierarchyInRect:afterScreenUpdates:|
-// has adverse flickering when taking a snapshot of the NTP while in the app
-// switcher.
-const base::Feature kSnapshotDrawView{"SnapshotDrawView",
-                                      base::FEATURE_DISABLED_BY_DEFAULT};
-
 const base::Feature kSettingsRefresh{"SettingsRefresh",
                                      base::FEATURE_DISABLED_BY_DEFAULT};
 

ios/chrome/browser/ui/ui_feature_flags.h

@@ -11,9 +11,6 @@
 // Feature to open tab switcher after sliding down the toolbar.
 extern const base::Feature kExpandedTabStrip;
 
-// Feature to take snapshots using |-drawViewHierarchy:|.
-extern const base::Feature kSnapshotDrawView;
-
 // Feature to apply UI Refresh theme to the settings.
 extern const base::Feature kSettingsRefresh;