Remove special wheel handling path from ScrollableArea

LayoutTests/fast/events/platform-wheelevent-paging-xy-in-scrolling-page.html

Index: LayoutTests/fast/events/platform-wheelevent-paging-xy-in-scrolling-page.html
diff --git a/LayoutTests/fast/events/platform-wheelevent-paging-xy-in-scrolling-page.html b/LayoutTests/fast/events/platform-wheelevent-paging-xy-in-scrolling-page.html
index 709b07b63ff15e42668aeb5137393aa5ba31545f..4d33acc9994c1a14c9959901afebb009c3e46307 100644
--- a/LayoutTests/fast/events/platform-wheelevent-paging-xy-in-scrolling-page.html
+++ b/LayoutTests/fast/events/platform-wheelevent-paging-xy-in-scrolling-page.html
@@ -4,8 +4,6 @@
         <script>
             var givenScrollTop = 2; // Only one page per event, so this should be interpreted as 1
             var givenScrollLeft = 2;
-            var expectedScrollTop = 511; // Window is 800x600. 15 pixel scrollbars. Scroll 87.5% of visible.
-            var expectedScrollLeft = 686;
             var event;
             var div;
 
@@ -27,8 +25,8 @@
 
             function checkOffsets()
             {
-                shouldBe("document.scrollingElement.scrollTop", "window.expectedScrollTop");
-                shouldBe("document.scrollingElement.scrollLeft", "window.expectedScrollLeft");
+                debug("document.scrollingElement.scrollTop = " + document.scrollingElement.scrollTop);
+                debug("document.scrollingElement.scrollLeft = " + document.scrollingElement.scrollLeft);

[bokan, 2015/08/19 12:42:47]

The expectation is platform dependent so we don't know the expected values here.

[Rick Byers, 2015/08/19 17:33:30]

Why did your CL change that though?  Are you intending to make the behavior more
platform dependent?  Ideally we should be setting up modes/inputs in layout
tests to be platform independent (but have multiple test cases for the different
behaviors possible in different platforms).

[bokan, 2015/08/19 18:45:46]

No, there's no change in the dependency on platform, I'm just fixing the
currently broken expectation (Mac has a separate expectation with a FAILing
output). The problem is that the value outputted is dependent on platform so I
don't think the test should be outputting PASS/FAIL (since it doesn't know what
the expected value is) - I made it output the value and the platform dependent
expectation tests for correctness.

[Rick Byers, 2015/08/19 19:42:09]

Sorry, I wrote this before seeing the test changes.  In general we rely on
shouldBe to indicate what we really expect, and 'debug' to indicate things that
can probably be blindly updated.  Ideally layout tests would have a way to set
or get the maxOverlapBetweenPages so we're not platform dependant, but adding
that is probably overkill.  What do you think about just hard-coding the
expected maxOverlapBetweenPages value in the test file, using a UA string check
to see if we're on Mac?  Then we could have a shouldBe that would PASS on all
platforms.

                 finishJSTest();
             }