Implement Middle Click Autoscroll on all platforms not just Windows

third_party/WebKit/LayoutTests/fast/events/panScroll-use-count.html

Index: third_party/WebKit/LayoutTests/fast/events/panScroll-use-count.html
diff --git a/third_party/WebKit/LayoutTests/fast/events/panScroll-use-count.html b/third_party/WebKit/LayoutTests/fast/events/panScroll-use-count.html
deleted file mode 100644
index 1f74345984e13a95766cacfc70f7622adf3e0e76..0000000000000000000000000000000000000000
--- a/third_party/WebKit/LayoutTests/fast/events/panScroll-use-count.html
+++ /dev/null
@@ -1,35 +0,0 @@
-<style type="text/css">
-#scrollable {
-    height: 1000px;
-    overflow: auto;
-    border: solid 3px #cc0000;
-    font-size: 80px;
-}
-</style>
-<script src="../../resources/testharness.js"></script>
-<script src="../../resources/testharnessreport.js"></script>
-<div id="container">
-<p id="description"></p>
-For manual testing, hold middle button in scrollable and move around mouse pointer for scrolling, then release middle button to stop scrolling.
-<div id="scrollable"></div>
-</div>
-<div id="console"></div>
-</body>
-<script>
-test(function() {
-    if (!window.eventSender)
-        return;
-    var middleButton = 1;
-    var panScrollRadius = 15;
-    var PanScrollingStart = 1551;
-    var scrollable = document.getElementById("scrollable");
-    var startX = scrollable.offsetLeft + 5;
-    var startY = scrollable.offsetTop + 5;
-    var endX = startX;
-    var endY = scrollable.offsetTop + panScrollRadius + 6;
-    eventSender.mouseMoveTo(startX, startY);
-    eventSender.mouseDown(middleButton);
-    eventSender.mouseMoveTo(endX, endY);
-    assert_true(internals.isUseCounted(document, PanScrollingStart));
-})
-</script>