Allow turning on selection painting without selection gaps via window.internals.

Source/core/testing/Internals.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  * Copyright (C) 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 2457 matching lines @@
         element->layoutObject()->addOutlineRects(rects, LayoutPoint());
     return ClientRectList::create(rects);
 }
 
 void Internals::setCapsLockState(bool enabled)
 {
     PlatformKeyboardEvent::setCurrentCapsLockState(enabled ?
         PlatformKeyboardEvent::OverrideCapsLockState::On : PlatformKeyboardEvent::OverrideCapsLockState::Off);
 }
 
+void Internals::setSelectionPaintingWithoutSelectionGapsEnabled(bool enabled)
+{
+    RuntimeEnabledFeatures::setSelectionPaintingWithoutSelectionGapsEnabled(enabled);
+}
+
 bool Internals::setScrollbarVisibilityInScrollableArea(Node* node, bool visible)
 {
     LayoutObject* layoutObject = node->layoutObject();
     if (!layoutObject)
         return false;
     DeprecatedPaintLayer* layer = layoutObject->enclosingLayer();
     if (!layer)
         return false;
     ScrollableArea* scrollableArea = layer->scrollableArea();
     if (!scrollableArea)
         return false;
     ScrollAnimator* animator = layer->scrollableArea()->scrollAnimator();
     if (!animator)
         return false;
 
     return animator->setScrollbarsVisibleForTesting(visible);
 }
 
 void Internals::forceRestrictIFramePermissions()
 {
     RuntimeEnabledFeatures::setRestrictIFramePermissionsEnabled(true);
 }
 
 } // namespace blink