Enable universal accelerated overflow scroll

Source/core/rendering/compositing/CompositingReasonFinder.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/rendering/compositing/CompositingReasonFinder.h"
 
 #include "CSSPropertyNames.h"
 #include "HTMLNames.h"
 #include "core/frame/FrameView.h"
@@ skipping 41 matching lines @@
     if (settings.acceleratedCompositingForCanvasEnabled())
         m_compositingTriggers |= CanvasTrigger;
     if (settings.acceleratedCompositingForAnimationEnabled())
         m_compositingTriggers |= AnimationTrigger;
     if (settings.compositedScrollingForFramesEnabled())
         m_compositingTriggers |= ScrollableInnerFrameTrigger;
     if (settings.acceleratedCompositingForFiltersEnabled())
         m_compositingTriggers |= FilterTrigger;
     if (settings.acceleratedCompositingForGpuRasterizationHintEnabled())
         m_compositingTriggers |= GPURasterizationTrigger;
-    if (settings.acceleratedCompositingForOverflowScrollEnabled())
-        m_compositingTriggers |= LegacyOverflowScrollTrigger;
-    if (settings.compositorDrivenAcceleratedScrollingEnabled())
+
+    // We map both these settings to universal overlow scrolling.
+    // FIXME: Replace these settings with a generic compositing setting for HighDPI.
+    if (settings.acceleratedCompositingForOverflowScrollEnabled() || settings.compositorDrivenAcceleratedScrollingEnabled())
         m_compositingTriggers |= OverflowScrollTrigger;
+
     // FIXME: acceleratedCompositingForFixedPositionEnabled should be renamed acceleratedCompositingForViewportConstrainedPositionEnabled().
     // Or the sticky and fixed position elements should be behind different flags.
     if (settings.acceleratedCompositingForFixedPositionEnabled())
         m_compositingTriggers |= ViewportConstrainedPositionedTrigger;
-
-    // FIXME: This monkeying with the accelerated triggers is temporary and should
-    // be removed once the feature ships.
-
-    // Currently, we must have the legacy path enabled to use the new path.
-    if (!(m_compositingTriggers & LegacyOverflowScrollTrigger))
-        m_compositingTriggers &= ~OverflowScrollTrigger;
-
-    // Enable universal overflow scrolling (and only universal overflow scrolling)
-    // on the new bleeding edge path. The above requirement (having legacy enabled)
-    // was only necessary to avoid explosions; the legacy path created far fewer
-    // layers. In the world of squashing, this doesn't make sense. We never want
-    // to use the old path in that case.
-    if (RuntimeEnabledFeatures::bleedingEdgeFastPathsEnabled()) {
-        m_compositingTriggers |= OverflowScrollTrigger;
-        m_compositingTriggers &= ~LegacyOverflowScrollTrigger;
-    }
 }
 
 bool CompositingReasonFinder::has3DTransformTrigger() const
 {
     return m_compositingTriggers & ThreeDTransformTrigger;
 }
 
 bool CompositingReasonFinder::hasAnimationTrigger() const
 {
     return m_compositingTriggers & AnimationTrigger;
@@ skipping 283 matching lines @@
                 *needToRecomputeCompositingRequirements = true;
             }
             return false;
         }
     }
 
     return true;
 }
 
 }