Add additional information to FAIL lines for animation interpolation tests

LayoutTests/animations/interpolation/resources/interpolation-test.js

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 248 matching lines @@
       if (!CSS.supports(params.property, expectation)) {
         return 'FAIL: [' + params.property + ': ' + expectation + '] is not supported';
       }
       var value = getComputedStyle(this).getPropertyValue(params.property);
       var result = '';
       var reason = '';
       if (expectation !== undefined) {
         var parsedExpectation = getComputedStyle(replica).getPropertyValue(params.property);
         var pass = normalizeValue(value) === normalizeValue(parsedExpectation);
         result = pass ? 'PASS: ' : 'FAIL: ';
-        reason = pass ? '' : ', expected [' + expectation + ']';
+        reason = pass ? '' : ', expected [' + expectation + ']' +
+            (expectation === parsedExpectation ? '' : ' (parsed as [' + sanitizeUrls(parsedExpectation) + '])');
         value = pass ? expectation : sanitizeUrls(value);
       }
       return result + params.property + ' from [' + params.from + '] to ' +
           '[' + params.to + '] was [' + value + ']' +
           ' at ' + fraction + reason;
     };
     target.convertToReference = function() {
       this.style[params.property] = getComputedStyle(this).getPropertyValue(params.property);
     };
     var easing = createEasing(fraction);
@@ skipping 85 matching lines @@
       finishTest();
     }, 10000);
   }
 
   window.runAsRefTest = runAsRefTest;
   window.testInterpolationAt = testInterpolationAt;
   window.assertInterpolation = assertInterpolation;
   window.convertToReference = convertToReference;
   window.afterTest = afterTest;
 })();