Refactor Scroll Customization to share cc::ScrollStateData with blink.

third_party/WebKit/Source/core/page/scrolling/ScrollState.idl

 // Copyright 2015 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.
 
 // https://docs.google.com/document/d/1VnvAqeWFG9JFZfgG5evBqrLGDZYRE5w6G5jEDORekPY
 
 [
-    Constructor(optional double deltaX = 0,
-                optional double deltaY = 0,
-                optional double deltaGranularity = 0,
-                optional double velocityX = 0,
-                optional double velocityY = 0,
-                optional boolean inInertialPhase = false,
-                optional boolean isBeginning = false,
-                optional boolean isEnding = false),
-    WillBeGarbageCollected,
-    RuntimeEnabled=ScrollCustomization
-] interface ScrollState {
+  Constructor(optional double deltaX = 0,
+      optional double deltaY = 0,
+      optional long startPositionX = 0,
+      optional long startPositionY = 0,
+      optional double velocityX = 0,
+      optional double velocityY = 0,
+      optional boolean isBeginning = false,
+      optional boolean inInertialPhase = false,
+      optional boolean isEnding = false,
+      optional boolean shouldPropagate = true,
+      optional boolean fromUserInput = false,
+      optional boolean isDirectManipulation = false,
+      optional double deltaGranularity = 0),

[Ian Vollick, 2016/02/08 18:30:35]

nit: Could we pass a dictionary? There are quite a few parameters here. Offline
Tim suggested we might have fewer ctor parameters and use setters to change
things after construction. That seems like a good idea and might simplify more
than just the JS ctor.

+  WillBeGarbageCollected,
+  RuntimeEnabled = ScrollCustomization,
+] interface ScrollState
+{
     readonly attribute double deltaX;
     readonly attribute double deltaY;
-    readonly attribute double deltaGranularity;
+    readonly attribute long startPositionX;
+    readonly attribute long startPositionY;
     readonly attribute double velocityX;
     readonly attribute double velocityY;
+    readonly attribute boolean isBeginning;
     readonly attribute boolean inInertialPhase;
     readonly attribute boolean isEnding;
-    readonly attribute boolean isBeginning;
+    readonly attribute boolean shouldPropagate;
     readonly attribute boolean fromUserInput;
-    readonly attribute boolean shouldPropagate;
+    readonly attribute boolean isDirectManipulation;
+    readonly attribute double deltaGranularity;
 
     [RaisesException] void consumeDelta(double x, double y);
     void distributeToScrollChainDescendant();
 };