Bug 1161634 - Enable the test_wheel_scroll on Linux as well. r=mstange

gfx/layers/apz/test/apz_test_native_event_utils.js

@@ -17,6 +17,7 @@ function nativeVerticalWheelEventMsg() {
   switch (getPlatform()) {
     case "windows": return 0x020A; // WM_MOUSEWHEEL
     case "mac": return 0; // value is unused, can be anything
+    case "linux": return 4; // value is unused, pass GDK_SCROLL_SMOOTH anyway
   }
   throw "Native wheel events not supported on platform " + getPlatform();
 }
@@ -25,6 +26,7 @@ function nativeHorizontalWheelEventMsg() {
   switch (getPlatform()) {
     case "windows": return 0x020E; // WM_MOUSEHWHEEL
     case "mac": return 0; // value is unused, can be anything
+    case "linux": return 4; // value is unused, pass GDK_SCROLL_SMOOTH anyway
   }
   throw "Native wheel events not supported on platform " + getPlatform();
 }

gfx/layers/apz/test/mochitest.ini

@@ -10,4 +10,4 @@ skip-if = toolkit != 'gonk'  # bug 991198
 [test_bug1151663.html]
 skip-if = toolkit != 'gonk'  # bug 991198
 [test_wheel_scroll.html]
-skip-if = toolkit != 'windows' && toolkit != 'cocoa'
+skip-if = (os == 'android') || (os == 'b2g') # wheel events not supported

gfx/layers/apz/test/test_wheel_scroll.html

@@ -99,8 +99,15 @@ function continueTest() {
   }
 }
 
+function startTest() {
+  // If we allow smooth scrolling the "smooth" scrolling may cause the page to
+  // glide past the scrollbox (which is supposed to stop the scrolling) and so
+  // we might end up at the bottom of the page.
+  SpecialPowers.pushPrefEnv({"set": [["general.smoothScroll", false]]}, continueTest);
+}
+
 SimpleTest.waitForExplicitFinish();
-SimpleTest.waitForFocus(continueTest, window);
+SimpleTest.waitForFocus(startTest, window);
 
 </script>
 </pre>