Add SelectionMode enum for setRangeText() in HTMLInputElement and HTMLTextAreaElement

LayoutTests/fast/forms/resources/common-setrangetext.js

Index: LayoutTests/fast/forms/resources/common-setrangetext.js
diff --git a/LayoutTests/fast/forms/resources/common-setrangetext.js b/LayoutTests/fast/forms/resources/common-setrangetext.js
index 6861347fab84f8211e1f9e7f54e47b0ab9bbacd6..7b05d2c60d8b93cde20e9eabdd6f68c22fc0b884 100644
--- a/LayoutTests/fast/forms/resources/common-setrangetext.js
+++ b/LayoutTests/fast/forms/resources/common-setrangetext.js
@@ -83,10 +83,10 @@ function runTestsShouldPass(tagName, attributes)
 
     evalAndLog("element.value = '0123456789'");
     evalAndLog("element.setSelectionRange(6, 9)");
-    evalAndLog("element.setRangeText('AB', 1, 1, 'invalid')"); // Invalid selectMode values default to preserve.
-    shouldBeEqualToString("element.value", "0AB123456789");
-    shouldBe("element.selectionStart", "8");
-    shouldBe("element.selectionEnd", "11");
+    shouldThrow("element.setRangeText('AB', 1, 1, 'invalid')"); // Invalid selectMode should throw TypeError
+    shouldBeEqualToString("element.value", "0123456789");
+    shouldBe("element.selectionStart", "6");
+    shouldBe("element.selectionEnd", "9");
 
     evalAndLog("element.value = '0123456789'");
     evalAndLog("element.setSelectionRange(6, 9)");