Move ScrollBehavior to ScrollTypes.h, so that ComputedStyle.h doesn't need to include ScrollableAre…

third_party/WebKit/Source/platform/scroll/ScrollTypes.h

Index: third_party/WebKit/Source/platform/scroll/ScrollTypes.h
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollTypes.h b/third_party/WebKit/Source/platform/scroll/ScrollTypes.h
index cd598cb801f80e2006b3c2b1c551d131dc1d1f01..2bfcd02b5ed6b040e70a4624c8aeccd2c1e364ae 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollTypes.h
+++ b/third_party/WebKit/Source/platform/scroll/ScrollTypes.h
@@ -183,6 +183,12 @@ enum ScrollbarOverlayStyle {
     ScrollbarOverlayStyleLight
 };
 
+enum ScrollBehavior {
+    ScrollBehaviorAuto,
+    ScrollBehaviorInstant,
+    ScrollBehaviorSmooth,
+};
+
 // The result of an attempt to scroll. If didScroll is true, then unusedScrollDelta gives
 // the amount of the scroll delta that was not consumed by scrolling.
 struct ScrollResult {