Since https://trac.webkit.org/changeset/198269 the layout test platform/gtk/scrollbars/main-frame-scrollbar-horizontal-wheel-scroll.html fails on platform GTK.

This is the diff image:

https://build.webkit.org/results/GTK%20Linux%2064-bit%20Release%20%28Tests%29/r203502%20%2817200%29/platform/gtk/scrollbars/main-frame-scrollbar-horizontal-wheel-scroll-diffs.html

As you can see, the expected results is that the window is scrolled to the right, but the actual result is not scrolling the window to the right.

Any of this two patches make the test pass:

--- a/LayoutTests/platform/gtk/scrollbars/main-frame-scrollbar-horizontal-wheel-scroll-expected.html
+++ b/LayoutTests/platform/gtk/scrollbars/main-frame-scrollbar-horizontal-wheel-scroll-expected.html
@@ -3,7 +3,7 @@
 <p>This is a test for bug <a href="https://bugs.webkit.org/show_bug.cgi?id=122859">122859</a>.
 Scrolling with the mouse wheel over the horizontal main scrollbar should scroll the view horizontally</p>
 <script>
-  document.scrollingElement.scrollLeft = 40;
+  document.scrollingElement.scrollLeft = 0;
 </script>
 </body>
 </html>


--- a/Source/WebCore/platform/ScrollAnimationSmooth.cpp
+++ b/Source/WebCore/platform/ScrollAnimationSmooth.cpp
@@ -254,7 +254,7 @@ static inline void getAnimationParametersForGranularity(ScrollGranularity granul
         maximumCoastTime = 1;
         break;
     case ScrollByPixel:
-        animationTime = 11 * tickTime;
+        animationTime = 1 * tickTime;
         repeatMinimumSustainTime = 2 * tickTime;
         attackTime = 3 * tickTime;
         releaseTime = 3 * tickTime;



However, I don't think any of them is right. 

Basically the first patch is disabling the horizontal scrolling on the expected result, and the second one is partially reverting r198269


So, I will mark this test as failing on the test expectations and leave here this bug.