Introduce panScrollTest() for simplify pan-scroll test scripts

LayoutTests/fast/events/resources/panScroll.js

+var autoscrollInterval = 50;
+var middleButton = 1;
+var panScrollRadius = 15; // from WebCore/platform/ScrollView.h
+
+window.jsTestIsAsync = true;
+
+function $(id)
+{
+    return document.getElementById(id);
+}
+
+function testPanScroll(param)
+{
+    function finishTest()
+    {
+        if ($('container'))
+            $('container').innerHTML = '';
+        if (param.finishTest)
+            param.finishTest();
+        if (window.finishJSTest) {
+            finishJSTest();
+            return;
+        }
+        if (window.testRunner)
+            testRunner.notifyDone();
+    }
+
+    var scrollable = param.scrollable;
+    var scrolledObject = param.scrolledObject || scrollable;
+
+    if (!scrollable.innerHTML) {
+        for (var i = 0; i < 100; ++i) {
+            var line = document.createElement('div');
+            line.innerHTML = "line " + i;
+            scrollable.appendChild(line);
+        }
+    }
+
+    var noModeScroll = false;
+    var scrolled = false;
+
+    scrolledObject.onscroll = function() {
+        if (noModeScroll) {
+            testFailed('still autoscroll');
+            finishTest();
+            return;
+        }
+
+        if (scrolled)
+            return;
+        scrolled = true;
+        testPassed('autoscroll started');
+
+        if (window.eventSender) {
+            if (param.clickOrDrag == 'click')
+                eventSender.mouseDown(middleButton);
+            eventSender.mouseUp(middleButton);
+        }
+    };
+
+    scrollable.ownerDocument.onmouseup = function(e) {
+        if (!scrolled || e.button != middleButton)
+            return;
+        noMoreScroll = true;
+        window.setTimeout(function() {
+            testPassed('autoscroll stopped');
+            finishTest();
+        }, autoscrollInterval * 2);
+    };
+
+    if (!window.eventSender)
+        return;
+    var startX = param.startX || scrollable.offsetLeft + 5;
+    var startY = param.startY || scrollable.offsetTop + 5;
+    var endX = param.endX || scrollable.offsetLeft + 5;
+    var endY = param.endY || scrollable.offsetTop + panScrollRadius + 6;
+    eventSender.mouseMoveTo(startX, startY);
+    eventSender.mouseDown(middleButton);
+    if (param.clickOrDrag == 'click')
+        eventSender.mouseUp(middleButton);
+    eventSender.mouseMoveTo(endX, endY);
+}