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

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

 "use strict";
 
 // Also test a selection with no ranges
 testRanges.unshift("[]");
 
 // Run a subset of all of extend tests.
 // Huge number of tests in a single file causes problems. Each of
 // extend-NN.html runs a part of them.
 //
 // startIndex - Start index in testRanges array
 // optionalEndIndex - End index in testRanges array + 1. If this argument is
 //     omitted, testRanges.length is applied.
 function testExtendSubSet(startIndex, optionalEndIndex) {
     var endIndex = optionalEndIndex === undefined ? testRanges.length : optionalEndIndex;
     if (startIndex < 0 || startIndex >= testRanges.length)
         throw "Sanity check: Specified index is invalid.";
     if (endIndex < 0 || endIndex > testRanges.length)
         throw "Sanity check: Specified index is invalid.";
 
     // We test Selections that go both forwards and backwards here.  In the
     // latter case we need to use extend() to force it to go backwards, which is
     // fair enough, since that's what we're testing.  We test collapsed
     // selections only once.
     for (var i = startIndex; i < endIndex; i++) {
         var endpoints = eval(testRanges[i]);
+        // We can't test extend() with unselectable endpoints.
+        if (!isSelectableNode(endpoints[0]) || !isSelectableNode(endpoints[2]))
+            continue;
         for (var j = 0; j < testPoints.length; j++) {
             if (endpoints[0] == endpoints[2]
             && endpoints[1] == endpoints[3]) {
                 // Test collapsed selections only once
                 test(function() {
                     setSelectionForwards(endpoints);
                     testExtend(endpoints, eval(testPoints[j]));
                 }, "extend() with range " + i + " " + testRanges[i]
                 + " and point " + j + " " + testPoints[j]);
             } else {
@@ skipping 113 matching lines @@
         assert_equals(getSelection().anchorOffset, offset,
             "anchorOffset must be the offset passed to extend() if the node has a different root from the original range");
     }
     assert_equals(getSelection().focusNode, node,
         "focusNode must be the node passed to extend()");
     assert_equals(getSelection().focusOffset, offset,
         "focusOffset must be the offset passed to extend()");
     assert_not_equals(getSelection().getRangeAt(0), originalRange,
         "extend() must replace any existing range with a new one, not mutate the existing one");
 }