Compute snap offsets (both repeat and element based)

third_party/WebKit/Source/core/dom/Document.cpp

Index: third_party/WebKit/Source/core/dom/Document.cpp
diff --git a/third_party/WebKit/Source/core/dom/Document.cpp b/third_party/WebKit/Source/core/dom/Document.cpp
index 45a91520ec31434010ac96e70b77e51e429b7f9c..6293a4abeed8f0b5e52058c55dc9d8c077ed3e28 100644
--- a/third_party/WebKit/Source/core/dom/Document.cpp
+++ b/third_party/WebKit/Source/core/dom/Document.cpp
@@ -195,6 +195,7 @@
 #include "core/page/PointerLockController.h"
 #include "core/page/scrolling/RootScroller.h"
 #include "core/page/scrolling/ScrollingCoordinator.h"
+#include "core/page/scrolling/SnapCoordinator.h"
 #include "core/svg/SVGDocumentExtensions.h"
 #include "core/svg/SVGTitleElement.h"
 #include "core/svg/SVGUseElement.h"
@@ -1635,6 +1636,9 @@ void Document::inheritHtmlAndBodyElementStyles(StyleRecalcChange change)
         columnGap = overflowStyle->columnGap();
     }
 
+    ScrollSnapType snapType = overflowStyle->getScrollSnapType();
+    const LengthPoint& snapDestination = overflowStyle->scrollSnapDestination();
+
     RefPtr<ComputedStyle> documentStyle = layoutView()->mutableStyle();
     if (documentStyle->getWritingMode() != rootWritingMode
         || documentStyle->direction() != rootDirection
@@ -1643,7 +1647,9 @@ void Document::inheritHtmlAndBodyElementStyles(StyleRecalcChange change)
         || documentStyle->imageRendering() != imageRendering
         || documentStyle->overflowX() != overflowX
         || documentStyle->overflowY() != overflowY
-        || documentStyle->columnGap() != columnGap) {
+        || documentStyle->columnGap() != columnGap
+        || documentStyle->getScrollSnapType() != snapType
+        || documentStyle->scrollSnapDestination() != snapDestination) {
         RefPtr<ComputedStyle> newStyle = ComputedStyle::clone(*documentStyle);
         newStyle->setWritingMode(rootWritingMode);
         newStyle->setDirection(rootDirection);
@@ -1653,6 +1659,8 @@ void Document::inheritHtmlAndBodyElementStyles(StyleRecalcChange change)
         newStyle->setOverflowX(overflowX);
         newStyle->setOverflowY(overflowY);
         newStyle->setColumnGap(columnGap);
+        newStyle->setScrollSnapType(snapType);
+        newStyle->setScrollSnapDestination(snapDestination);
         layoutView()->setStyle(newStyle);
         setupFontBuilder(*newStyle);
     }
@@ -5518,6 +5526,14 @@ bool Document::threadedParsingEnabledForTesting()
     return s_threadedParsingEnabledForTesting;
 }
 
+SnapCoordinator* Document::snapCoordinator()
+{
+    if (RuntimeEnabledFeatures::cssScrollSnapPointsEnabled() && !m_snapCoordinator)
+        m_snapCoordinator = SnapCoordinator::create();
+
+    return m_snapCoordinator.get();
+}
+
 void Document::setContextFeatures(ContextFeatures& features)
 {
     m_contextFeatures = &features;
@@ -5959,6 +5975,7 @@ DEFINE_TRACE(Document)
     visitor->trace(m_canvasFontCache);
     visitor->trace(m_intersectionObserverController);
     visitor->trace(m_intersectionObserverData);
+    visitor->trace(m_snapCoordinator);
     Supplementable<Document>::trace(visitor);
     TreeScope::trace(visitor);
     ContainerNode::trace(visitor);