selection: Do not run invalid sub-tests with unselectable Range.

third_party/WebKit/LayoutTests/external/wpt/selection/addRange.js

 "use strict";
 
 function testAddRange(exception, range, endpoints, qualifier, testName) {
+    if (!isSelectableNode(endpoints[0]) || !isSelectableNode(endpoints[2])) {
+        test(function() {
+            assert_equals(exception, null, "Test setup must not throw exceptions");
+
+            assertSelectionNoChange(function() { selection.addRange(range); });
+            assert_equals(range.startContainer, endpoints[0],
+                "addRange() must not modify the startContainer of the Range it's given");
+            assert_equals(range.startOffset, endpoints[1],
+                "addRange() must not modify the startOffset of the Range it's given");
+            assert_equals(range.endContainer, endpoints[2],
+                "addRange() must not modify the endContainer of the Range it's given");
+            assert_equals(range.endOffset, endpoints[3],
+                "addRange() must not modify the endOffset of the Range it's given");
+        }, testName + ": " + qualifier + " addRange() must do nothing");
+        return;
+    }
+
     test(function() {
         assert_equals(exception, null, "Test setup must not throw exceptions");
 
         selection.addRange(range);
 
         assert_equals(range.startContainer, endpoints[0],
             "addRange() must not modify the startContainer of the Range it's given");
         assert_equals(range.startOffset, endpoints[1],
             "addRange() must not modify the startOffset of the Range it's given");
         assert_equals(range.endContainer, endpoints[2],
@@ skipping 155 matching lines @@
                     throw "Sanity check: the second Range we created must have the desired endContainer";
                 }
                 if (range2.endOffset !== endpoints2[3]) {
                     throw "Sanity check: the second Range we created must have the desired endOffset";
                 }
             } catch (e) {
                 exception = e;
             }
 
             testAddRange(exception, range1, endpoints1, "first", testName);
-            testAddRange(exception, range2, endpoints2, "second", testName);
+            if (selection.rangeCount > 0)
+                testAddRange(exception, range2, endpoints2, "second", testName);
         }
     }
 }