Bug 1685962 - Fix test_bug549170.html to work on Linux with the native theme. r=spohl

Differential Revision: https://phabricator.services.mozilla.com/D101325

layout/forms/test/mochitest.ini

@@ -26,7 +26,6 @@ skip-if = toolkit == 'android' # Bug 1658807
 [test_bug534785.html]
 [test_bug542914.html]
 [test_bug549170.html]
-fail-if = (os == 'linux' && os_version == '18.04' && !headless) # Bug 1599984
 [test_bug562447.html]
 [test_bug563642.html]
 [test_bug564115.html]

layout/forms/test/test_bug549170.html

@@ -32,30 +32,33 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=549170
 
 /** Test for Bug 549170 **/
 
-var gNumberOfMouseEventsCatched = 0;
+var gNumberOfMouseEventsCaught = 0;
 
 SimpleTest.waitForExplicitFinish();
 
 function mouseHandler(aEvent)
 {
-  gNumberOfMouseEventsCatched++;
+  gNumberOfMouseEventsCaught++;
   is(SpecialPowers.wrap(aEvent).originalTarget.nodeName, "DIV", "An inner div should be the target of the event");
   ok(SpecialPowers.wrap(aEvent).originalTarget.implementedPseudoElement == "::-moz-text-control-editing-root", "the target div should be the editor div");
 }
 
 function checkMouseEvents(element)
 {
-  gNumberOfMouseEventsCatched = 0;
+  gNumberOfMouseEventsCaught = 0;
 
-  synthesizeMouse(element, 7, 7, {type: "mousedown", button: 0});
-  synthesizeMouse(element, 7, 7, {type: "mouseup",   button: 0});
-  synthesizeMouse(element, 7, 7, {type: "mousedown", button: 1});
+  let x = element.offsetWidth / 2;
+  let y = element.offsetHeight / 2;
+
+  synthesizeMouse(element, x, y, {type: "mousedown", button: 0});
+  synthesizeMouse(element, x, y, {type: "mouseup",   button: 0});
+  synthesizeMouse(element, x, y, {type: "mousedown", button: 1});
   // NOTE: this event is going to copy the buffer on linux, this should not be a problem
-  synthesizeMouse(element, 7, 7, {type: "mouseup",   button: 1});
-  synthesizeMouse(element, 7, 7, {type: "mousedown", button: 2});
-  synthesizeMouse(element, 7, 7, {type: "mouseup",   button: 2});
+  synthesizeMouse(element, x, y, {type: "mouseup",   button: 1});
+  synthesizeMouse(element, x, y, {type: "mousedown", button: 2});
+  synthesizeMouse(element, x, y, {type: "mouseup",   button: 2});
 
-  is(gNumberOfMouseEventsCatched, 6, "Some mouse events have not been catched");
+  is(gNumberOfMouseEventsCaught, 6, "Some mouse events have not been caught");
 }
 
 function runTests()