Handle nested position:sticky elements correctly (compositor)

third_party/WebKit/Source/core/page/scrolling/StickyPositionScrollingConstraints.h

Index: third_party/WebKit/Source/core/page/scrolling/StickyPositionScrollingConstraints.h
diff --git a/third_party/WebKit/Source/core/page/scrolling/StickyPositionScrollingConstraints.h b/third_party/WebKit/Source/core/page/scrolling/StickyPositionScrollingConstraints.h
index 84dab3cc2f76ad7170d18bed9235375e5dc16c62..c31d9e89ab371e497a0c2ca1fe1c5e82168651c9 100644
--- a/third_party/WebKit/Source/core/page/scrolling/StickyPositionScrollingConstraints.h
+++ b/third_party/WebKit/Source/core/page/scrolling/StickyPositionScrollingConstraints.h
@@ -48,7 +48,8 @@ class StickyPositionScrollingConstraints final {
             other.m_nearestStickyBoxShiftingContainingBlock),
         m_totalStickyBoxStickyOffset(other.m_totalStickyBoxStickyOffset),
         m_totalContainingBlockStickyOffset(
-            other.m_totalContainingBlockStickyOffset) {}
+            other.m_totalContainingBlockStickyOffset),
+        m_localStickyOffset(other.m_localStickyOffset) {}
 
   FloatSize computeStickyOffset(
       const FloatRect& viewportRect,
@@ -113,6 +114,12 @@ class StickyPositionScrollingConstraints final {
     return m_totalContainingBlockStickyOffset;
   }
 
+  const LayoutBoxModelObject* nearestStickyAncestor() const {
+    return m_nearestStickyBoxShiftingStickyBox
+               ? m_nearestStickyBoxShiftingStickyBox
+               : m_nearestStickyBoxShiftingContainingBlock;
+  }
+
   bool operator==(const StickyPositionScrollingConstraints& other) const {
     return m_leftOffset == other.m_leftOffset &&
            m_rightOffset == other.m_rightOffset &&
@@ -128,7 +135,8 @@ class StickyPositionScrollingConstraints final {
                other.m_nearestStickyBoxShiftingContainingBlock &&
            m_totalStickyBoxStickyOffset == other.m_totalStickyBoxStickyOffset &&
            m_totalContainingBlockStickyOffset ==
-               other.m_totalContainingBlockStickyOffset;
+               other.m_totalContainingBlockStickyOffset &&
+           m_localStickyOffset == other.m_localStickyOffset;
   }
 
   bool operator!=(const StickyPositionScrollingConstraints& other) const {
@@ -163,6 +171,8 @@ class StickyPositionScrollingConstraints final {
   // LayoutBoxModelObjectTest.cpp.
   FloatSize m_totalStickyBoxStickyOffset;
   FloatSize m_totalContainingBlockStickyOffset;
+
+  FloatSize m_localStickyOffset;

[flackr, 2017/03/17 15:01:56]

This seems unused, remove it?

[smcgruer, 2017/03/17 17:36:52]

Done.

 };
 
 }  // namespace blink