Honor the wheel event canScroll bit instead of trying to infer it from the ctrl modifier

LayoutTests/fast/events/wheelevent-ctrl.html

Index: LayoutTests/fast/events/wheelevent-ctrl.html
diff --git a/LayoutTests/fast/events/wheelevent-ctrl.html b/LayoutTests/fast/events/wheelevent-ctrl.html
index 6b2b45537a9a18b895899062a2620e9274450939..7d19155207592695e012b1104f037f02d8971709 100644
--- a/LayoutTests/fast/events/wheelevent-ctrl.html
+++ b/LayoutTests/fast/events/wheelevent-ctrl.html
@@ -20,16 +20,16 @@ function runTest() {
 
     debug('Test mousewheel events over scrollable div');

[tdresser, 2014/11/27 15:06:09]

Can we write a test which has different expectations per platform, indicating
the difference in behavior?

[Rick Byers, 2014/11/27 18:05:54]

Layout tests really test only blink (at least in terms of the input code path),
and the blink behavior is identical between platforms.  So I don't think we want
different expectations per platform.

You could argue though that we should test all the different forms of input used
by different platforms.  Eg. here we're testing only ctrl==suppressScroll. 
Perhaps it would be good to add a 3rd case to emulate mac / CrOS touchpad with
ctrl set but NOT suppressScroll and verify it behaves identically to when ctrl
isn't set.  We don't normally write tests for code that could exist but doesn't
(eg. why not also check for Alt wheel?).  But in this case since we're changing
from one behavior to another, it's not unreasonable to verify that the old
behavior is no longer true.

Thoughts?

[lanwei, 2014/12/02 15:48:10]

Done.

 
-    debug('With ctrl modifier set');
+    debug('With ctrl modifier set and suppressScroll set to be true');
     wheelEventCount = 0;
     eventSender.mouseMoveTo(testDiv.offsetLeft + 5, testDiv.offsetTop + 5);
-    eventSender.mouseScrollBy(0, scrollAmount, false, true, "ctrlKey");
+    eventSender.mouseScrollBy(0, scrollAmount, false, true, "ctrlKey", true);
     shouldBe("wheelEventCount", "1");
     shouldEvaluateTo("deltaY", expectedDeltaY);
     shouldBeTrue("ctrlKey");
     shouldBe("testDiv.scrollTop", "0");
 
-    debug('Without ctrl');
+    debug('Without ctrl and suppressScroll set to be default false');
     wheelEventCount = 0;
     eventSender.mouseMoveTo(testDiv.offsetLeft + 5, testDiv.offsetTop + 5);
     eventSender.mouseScrollBy(0, scrollAmount, false, true);
@@ -42,16 +42,16 @@ function runTest() {
     debug('Test mousewheel events over the document');
     testDiv = document.getElementById('target2');
 
-    debug('With ctrl modifier set');
+    debug('With ctrl modifier set and suppressScroll set to be true');
     wheelEventCount = 0;
     eventSender.mouseMoveTo(testDiv.offsetLeft + 5, testDiv.offsetTop + 5);
-    eventSender.mouseScrollBy(0, scrollAmount, false, true, "ctrlKey");
+    eventSender.mouseScrollBy(0, scrollAmount, false, true, "ctrlKey", true);
     shouldBe("wheelEventCount", "1");
     shouldEvaluateTo("deltaY", expectedDeltaY);
     shouldBeTrue("ctrlKey");
-    shouldBe("document.body.scrollTop", "0");
+    shouldBe("window.scrollY", "0");
     
-    debug('Now without ctrl');
+    debug('Now without ctrl and suppressScroll set to be default false');
     wheelEventCount = 0;
     eventSender.mouseMoveTo(testDiv.offsetLeft + 5, testDiv.offsetTop + 5);
     eventSender.mouseScrollBy(0, scrollAmount, false, true);