Allow postponed rail application for touch scrolling - blink side.

Source/platform/PlatformGestureEvent.h

Index: Source/platform/PlatformGestureEvent.h
diff --git a/Source/platform/PlatformGestureEvent.h b/Source/platform/PlatformGestureEvent.h
index a1d8be5e0506953525615d3b62812b9567fb318b..7495f0fb7871f9472f042b48fa9cabdda3b7c84a 100644
--- a/Source/platform/PlatformGestureEvent.h
+++ b/Source/platform/PlatformGestureEvent.h
@@ -55,7 +55,7 @@ public:
     }
 
     void setScrollGestureData(float deltaX, float deltaY, float velocityX, float velocityY,
-        bool inertial, bool preventPropagation)
+        bool inertial, bool preventPropagation, RailsMode railsMode)
     {
         ASSERT(type() == PlatformEvent::GestureScrollBegin
             || type() == PlatformEvent::GestureScrollUpdate
@@ -66,6 +66,7 @@ public:
             ASSERT(velocityX == 0);
             ASSERT(velocityY == 0);
             ASSERT(!preventPropagation);
+            ASSERT(railsMode == PlatformEvent::RailsModeFree);
         }
 
         if (type() == PlatformEvent::GestureScrollBegin)
@@ -77,6 +78,7 @@ public:
         m_data.m_scroll.m_velocityY = velocityY;
         m_data.m_scroll.m_inertial = inertial;
         m_data.m_scroll.m_preventPropagation = preventPropagation;
+        m_data.m_scroll.m_railsMode = railsMode;
     }
 
     const IntPoint& position() const { return m_position; } // PlatformWindow coordinates.
@@ -114,6 +116,12 @@ public:
         return m_data.m_scroll.m_velocityY;
     }
 
+    RailsMode railsMode() const
+    {
+        ASSERT(m_type == PlatformEvent::GestureScrollUpdate);
+        return m_data.m_scroll.m_railsMode;
+    }
+
     bool inertial() const
     {
         ASSERT(m_type == PlatformEvent::GestureScrollUpdate || m_type == PlatformEvent::GestureScrollEnd);
@@ -185,6 +193,7 @@ protected:
             float m_velocityY;
             int m_preventPropagation;
             bool m_inertial;
+            RailsMode m_railsMode;
         } m_scroll;
 
         struct {