[No submit][SPInvalidation] Track paint offset change

third_party/WebKit/Source/core/paint/ObjectPaintInvalidator.cpp

 // Copyright 2016 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 "core/paint/ObjectPaintInvalidator.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/layout/LayoutView.h"
 #include "core/layout/api/LayoutPartItem.h"
@@ skipping 511 matching lines @@
 PaintInvalidationReason
 ObjectPaintInvalidatorWithContext::invalidatePaintIfNeededWithComputedReason(
     PaintInvalidationReason reason) {
   // We need to invalidate the selection before checking for whether we are
   // doing a full invalidation.  This is because we need to update the previous
   // selection rect regardless.
   invalidateSelectionIfNeeded(reason);
 
   switch (reason) {
     case PaintInvalidationNone:
-      // TODO(trchen): Currently we don't keep track of paint offset of layout
-      // objects.  There are corner cases that the display items need to be
-      // invalidated for paint offset mutation, but incurs no pixel difference
-      // (i.e. bounds stay the same) so no rect-based invalidation is issued.
-      // See crbug.com/508383 and crbug.com/515977.  This is a workaround to
-      // force display items to update paint offset. Exclude non-root SVG whose
-      // paint offset is always zero.
-      if ((!m_object.isSVG() || m_object.isSVGRoot()) &&
-          (m_context.forcedSubtreeInvalidationFlags &
-           PaintInvalidatorContext::ForcedSubtreeInvalidationChecking)) {
-        reason = PaintInvalidationLocationChange;
-        break;
+      // There are corner cases that the display items need to be invalidated
+      // for paint offset mutation, but incurs no pixel difference (i.e. bounds
+      // stay the same) so no rect-based invalidation is issued. See
+      // crbug.com/508383 and crbug.com/515977.
+      if (m_context.forcedSubtreeInvalidationFlags &
+          PaintInvalidatorContext::ForcedSubtreeInvalidationChecking) {
+        if (RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled()) {
+          if (m_context.oldPaintOffset != m_context.newPaintOffset) {
+            reason = PaintInvalidationLocationChange;
+            break;
+          }
+        } else {
+          // For non-SlimmingPaintInvalidation, we conservatively assume the
+          // object changed paint offset except for non-root SVG whose paint
+          // offset is always zero.
+          if (!m_object.isSVG() || m_object.isSVGRoot()) {
+            reason = PaintInvalidationLocationChange;
+            break;
+          }
+        }
       }
+
       if (m_object.isSVG() &&
           (m_context.forcedSubtreeInvalidationFlags &
            PaintInvalidatorContext::ForcedSubtreeSVGResourceChange)) {
         reason = PaintInvalidationSVGResourceChange;
         break;
       }
       return PaintInvalidationNone;
     case PaintInvalidationDelayedFull:
       return PaintInvalidationDelayedFull;
     default:
       DCHECK(isImmediateFullPaintInvalidationReason(reason));
       fullyInvalidatePaint(reason, m_context.oldVisualRect,
                            m_context.newVisualRect);
   }
 
   m_context.paintingLayer->setNeedsRepaint();
   m_object.invalidateDisplayItemClients(reason);
   return reason;
 }
 
 DisablePaintInvalidationStateAsserts::DisablePaintInvalidationStateAsserts()
     : m_disabler(&gDisablePaintInvalidationStateAsserts, true) {}
 
 }  // namespace blink