[SPInvalidation] Fix fixed-position printing

third_party/WebKit/Source/core/paint/PaintLayerPainter.h

 // 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.
 
 #ifndef PaintLayerPainter_h
 #define PaintLayerPainter_h
 
 #include "core/CoreExport.h"
 #include "core/paint/PaintLayerFragment.h"
 #include "core/paint/PaintLayerPaintingInfo.h"
@@ skipping 38 matching lines @@
                                  PaintLayerFlags,
                                  FragmentPolicy = AllowMultipleFragments);
 
   void paintOverlayScrollbars(GraphicsContext&,
                               const LayoutRect& damageRect,
                               const GlobalPaintFlags);
 
  private:
   enum ClipState { HasNotClipped, HasClipped };
 
-  bool collectPaintFragmentsForPaginatedFixedPosition(
-      const PaintLayerPaintingInfo&,
-      PaintLayerFragments&);
+  inline bool isFixedPositionObjectInPagedMedia();
+  void repeatFixedPositionObjectInPages(const PaintLayerPaintingInfo&,

[chrishtr, 2017/01/03 18:53:10]

The input for repeatFixedPositionObjectInPages must be a single
fragment that is then repeated. How about changing the signature
to enforce that? e.g. input is PaintLayerFragment and output is
PaintLayerFragments.

Also, this fixed-pos code seems pretty hacky (not your fault, it
was like that before). It would be good to fold it into
collectFragments somehow, add a TODO?

[Xianzhu, 2017/01/03 19:54:42]

Done.
Done.

Actually I reviewed the original change adding the fixed-position hack. For now
the hack (instead of folded into collectFragment) it's still needed because of
the specialty of the transformed path.

+                                        PaintLayerFragments&);
 
   PaintResult paintLayerContentsCompositingAllPhases(
       GraphicsContext&,
       const PaintLayerPaintingInfo&,
       PaintLayerFlags,
       FragmentPolicy = AllowMultipleFragments);
   PaintResult paintLayerWithTransform(GraphicsContext&,
                                       const PaintLayerPaintingInfo&,
                                       PaintLayerFlags);
   PaintResult paintFragmentByApplyingTransform(
@@ skipping 70 matching lines @@
   FRIEND_TEST_ALL_PREFIXES(PaintLayerPainterTest,
                            DontPaintWithTinyOpacityAndBackdropFilter);
   FRIEND_TEST_ALL_PREFIXES(PaintLayerPainterTest,
                            DoPaintWithCompositedTinyOpacity);
   FRIEND_TEST_ALL_PREFIXES(PaintLayerPainterTest, DoPaintWithNonTinyOpacity);
 };
 
 }  // namespace blink
 
 #endif  // PaintLayerPainter_h