Implement CSS: scroll-boundary-behavior

cc/input/scroll_boundary_behavior.h

+// Copyright (c) 2017 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.
+
+#ifndef CC_INPUT_SCROLL_BOUNDARY_BEHAVIOR_H_
+#define CC_INPUT_SCROLL_BOUNDARY_BEHAVIOR_H_
+
+#include "cc/cc_export.h"
+
+namespace cc {
+
+struct CC_EXPORT ScrollBoundaryBehavior {
+  enum ScrollBoundaryBehaviorType {
+    kScrollBoundaryBehaviorTypeAuto,
+    kScrollBoundaryBehaviorTypeContain,
+    kScrollBoundaryBehaviorTypeNone

[ajuma, 2017/06/30 20:46:49]

Please add brief comments about what these values mean.

[sunyunjia, 2017/07/14 02:59:00]

Done.

+  };
+
+  ScrollBoundaryBehavior()
+      : x(kScrollBoundaryBehaviorTypeAuto),
+        y(kScrollBoundaryBehaviorTypeAuto) {}
+  explicit ScrollBoundaryBehavior(ScrollBoundaryBehaviorType type)
+      : x(type), y(type) {}
+  ScrollBoundaryBehavior(ScrollBoundaryBehaviorType x_type,
+                         ScrollBoundaryBehaviorType y_type)
+      : x(x_type), y(y_type) {}
+
+  ScrollBoundaryBehaviorType x;
+  ScrollBoundaryBehaviorType y;
+
+  bool operator==(const ScrollBoundaryBehavior& a) const {
+    return (a.x == x) && (a.y == y);
+  }
+  bool operator!=(const ScrollBoundaryBehavior& a) const {
+    return !(*this == a);
+  }
+};
+
+}  // namespace cc
+
+#endif  // CC_INPUT_SCROLL_BOUNDARY_BEHAVIOR_H_