Bug 1123514 - Add test for wrong offset calculation; r=esawin

Add a test that creates conditions for wrong offset calculation and
potentially causes an exception.

mobile/android/tests/browser/robocop/robocop_input.html

@@ -127,6 +127,17 @@
           setSelection(3); // Offsets that testInputConnection.java expects.
         },
 
+        test_bug1123514: function() {
+          document.activeElement.addEventListener('input', function test_bug1123514_listener() {
+            this.removeEventListener('input', test_bug1123514_listener);
+
+            // Only works on input and textarea.
+            if (this.value === 'b') {
+              this.value = 'abc';
+            }
+          });
+        },
+
         focus_resetting_input: function(val) {
           resetting_input.value = val;
           resetting_input.focus();

mobile/android/tests/browser/robocop/src/org/mozilla/gecko/tests/testInputConnection.java

@@ -243,6 +243,19 @@ public class testInputConnection extends JavascriptBridgeTest {
             ic.deleteSurroundingText(0, 2);
             assertTextAndSelectionAt("Can clear text", ic, "", 0);
 
+            // Bug 1123514 - exception due to incorrect text replacement offsets.
+            getJS().syncCall("test_bug1123514");
+            // Gecko will change text to 'abc' when we input 'b', potentially causing
+            // incorrect calculation of text replacement offsets.
+            ic.commitText("b", 1);
+            // We don't assert text here because this test only works for input/textarea,
+            // so an assertion would fail for contentEditable/designMode.
+            processGeckoEvents();
+            processInputConnectionEvents();
+
+            ic.deleteSurroundingText(2, 1);
+            assertTextAndSelectionAt("Can clear text", ic, "", 0);
+
             // Make sure we don't leave behind stale events for the following test.
             processGeckoEvents();
             processInputConnectionEvents();