Compute snap offsets (both repeat and element based)

Source/core/frame/LocalFrame.cpp

Index: Source/core/frame/LocalFrame.cpp
diff --git a/Source/core/frame/LocalFrame.cpp b/Source/core/frame/LocalFrame.cpp
index 8951fe2f267717a56e37cff755ff3f4a80e0f8ab..d33b6b0461bcd1d68c3d518ab16020b9aa489e43 100644
--- a/Source/core/frame/LocalFrame.cpp
+++ b/Source/core/frame/LocalFrame.cpp
@@ -61,6 +61,7 @@
 #include "core/page/FocusController.h"
 #include "core/page/Page.h"
 #include "core/page/scrolling/ScrollingCoordinator.h"
+#include "core/page/scrolling/SnapCoordinator.h"
 #include "core/paint/DeprecatedPaintLayer.h"
 #include "core/paint/TransformRecorder.h"
 #include "core/svg/SVGDocumentExtensions.h"
@@ -217,6 +218,7 @@ DEFINE_TRACE(LocalFrame)
     visitor->trace(m_eventHandler);
     visitor->trace(m_console);
     visitor->trace(m_inputMethodController);
+    visitor->trace(m_snapCoordinator);
     visitor->template registerWeakMembers<LocalFrame, &LocalFrame::clearWeakMembers>(this);
     HeapSupplementable<LocalFrame>::trace(visitor);
 #endif
@@ -852,6 +854,9 @@ inline LocalFrame::LocalFrame(FrameLoaderClient* client, FrameHost* host, FrameO
     , m_textZoomFactor(parentTextZoomFactor(this))
     , m_inViewSourceMode(false)
 {
+    if (RuntimeEnabledFeatures::cssScrollSnapPointsEnabled())
+        m_snapCoordinator = SnapCoordinator::create(*this);

[esprehn, 2015/09/24 17:37:41]

This should be on FrameView.

[majidvp, 2015/10/15 21:47:02]

Following your other comment I moved it to document which I think is a more
appropriate owner. wdyt? 

+
     if (isLocalRoot())
         m_instrumentingAgents = InstrumentingAgents::create();
     else