Bug 1825054 - Don't get stuck in endless loop when getting bounds. r=morgan

Differential Revision: https://phabricator.services.mozilla.com/D173864

accessible/base/TextLeafRange.cpp

@@ -1782,7 +1782,9 @@ LayoutDeviceIntRect TextLeafRange::Bounds() const {
         nsIAccessibleText::BOUNDARY_LINE_START, eDirNext);
     TextLeafPoint lastPointInLine = lineStartPoint.FindBoundary(
         nsIAccessibleText::BOUNDARY_CHAR, eDirPrevious);
-    if (mEnd <= lastPointInLine) {
+    // If currPoint is the end of the document, lineStartPoint will be equal
+    // to currPoint and we would be in an endless loop.
+    if (lineStartPoint == currPoint || mEnd <= lastPointInLine) {
       lastPointInLine = mEnd;
       locatedFinalLine = true;
     }

accessible/tests/browser/mac/browser_text_basics.js

@@ -378,3 +378,22 @@ addAccessibleTask(
     is(str, "hello", "Left word at start of input should be right word");
   }
 );
+
+addAccessibleTask(`<p id="p">hello world</p>`, async (browser, accDoc) => {
+  let macDoc = accDoc.nativeInterface.QueryInterface(
+    Ci.nsIAccessibleMacInterface
+  );
+
+  let p = getNativeInterface(accDoc, "p");
+  let range = macDoc.getParameterizedAttributeValue(
+    "AXTextMarkerRangeForUIElement",
+    p
+  );
+
+  let bounds = macDoc.getParameterizedAttributeValue(
+    "AXBoundsForTextMarkerRange",
+    range
+  );
+
+  ok(bounds.origin && bounds.size, "Returned valid bounds");
+});