Bug 1379808 - Intermittent browser_test_zoom_text.js failure, wrong height and y, r=eeejay

accessible/tests/browser/bounds/browser.ini

@@ -8,4 +8,3 @@ support-files =
 
 [browser_test_zoom.js]
 [browser_test_zoom_text.js]
-skip-if = true # Bug 1372296, Bug 1379808, Bug 1391453

accessible/tests/mochitest/common.js

@@ -191,6 +191,19 @@ function isObject(aObj, aExpectedObj, aMsg) {
             "', expected '" + prettyName(aExpectedObj) + "'");
 }
 
+/**
+ * is() function checking the expected value is within the range.
+ */
+function isWithin(aExpected, aGot, aWithin, aMsg)
+{
+  if (Math.abs(aGot - aExpected) <= aWithin) {
+    ok(true, `${aMsg} - Got ${aGot}`);
+  } else {
+    ok(false,
+       `${aMsg} - Got ${aGot}, expected ${aExpected} with error of ${aWithin}`);
+  }
+}
+
 // //////////////////////////////////////////////////////////////////////////////
 // Helpers for getting DOM node/accessible
 

accessible/tests/mochitest/layout.js

@@ -150,13 +150,18 @@ function testTextBounds(aID, aStartOffset, aEndOffset, aRect, aCoordOrigin) {
   var hyperText = getAccessible(aID, [nsIAccessibleText]);
   hyperText.getRangeExtents(aStartOffset, aEndOffset,
                             xObj, yObj, widthObj, heightObj, aCoordOrigin);
+
+  // x
   is(xObj.value, expectedX,
      "Wrong x coordinate of text between offsets (" + aStartOffset + ", " +
      aEndOffset + ") for " + prettyName(aID));
-  is(yObj.value, expectedY,
-     "Wrong y coordinate of text between offsets (" + aStartOffset + ", " +
-     aEndOffset + ") for " + prettyName(aID));
 
+  // y
+  isWithin(yObj.value, expectedY, 1,
+           `y coord of text between offsets (${aStartOffset}, ${aEndOffset}) ` +
+           `for ${prettyName(aID)}`);
+
+  // Width
   var msg = "Wrong width of text between offsets (" + aStartOffset + ", " +
     aEndOffset + ") for " + prettyName(aID);
   if (widthObj.value == expectedWidth)
@@ -164,9 +169,10 @@ function testTextBounds(aID, aStartOffset, aEndOffset, aRect, aCoordOrigin) {
   else
     todo(false, msg); // fails on some windows machines
 
-  is(heightObj.value, expectedHeight,
-     "Wrong height of text between offsets (" + aStartOffset + ", " +
-     aEndOffset + ") for " + prettyName(aID));
+  // Height
+  isWithin(heightObj.value, expectedHeight, 1,
+           `height of text between offsets (${aStartOffset}, ${aEndOffset}) ` +
+           `for ${prettyName(aID)}`);
 }
 
 /**