bindings: Make the sequence conversion code more complaint with WebIDL.

third_party/WebKit/LayoutTests/external/wpt/web-animations/interfaces/KeyframeEffect/processing-a-keyframes-argument-expected.txt

 This is a testharness.js-based test.
-Found 50 tests; 34 PASS, 16 FAIL, 0 TIMEOUT, 0 NOTRUN.
+Found 50 tests; 35 PASS, 15 FAIL, 0 TIMEOUT, 0 NOTRUN.
 PASS non-animatable property 'animation' is not accessed when using a property-indexed keyframe object 
 PASS non-animatable property 'animationDelay' is not accessed when using a property-indexed keyframe object 
 PASS non-animatable property 'animationDirection' is not accessed when using a property-indexed keyframe object 
 PASS non-animatable property 'animationDuration' is not accessed when using a property-indexed keyframe object 
 PASS non-animatable property 'animationFillMode' is not accessed when using a property-indexed keyframe object 
 PASS non-animatable property 'animationIterationCount' is not accessed when using a property-indexed keyframe object 
 PASS non-animatable property 'animationName' is not accessed when using a property-indexed keyframe object 
 PASS non-animatable property 'animationPlayState' is not accessed when using a property-indexed keyframe object 
 PASS non-animatable property 'animationTimingFunction' is not accessed when using a property-indexed keyframe object 
 PASS non-animatable property 'transition' is not accessed when using a property-indexed keyframe object 
@@ skipping 24 matching lines @@
 FAIL Equivalent property indexed and sequenced keyframes: two properties with one value (intermediate value).getKeyframes is not a function
 FAIL Equivalent property indexed and sequenced keyframes: two properties with three values (intermediate value).getKeyframes is not a function
 FAIL Equivalent property indexed and sequenced keyframes: two properties with different numbers of values (intermediate value).getKeyframes is not a function
 FAIL Equivalent property indexed and sequenced keyframes: same offset applied to all keyframes (intermediate value).getKeyframes is not a function
 FAIL Equivalent property indexed and sequenced keyframes: same easing applied to all keyframes (intermediate value).getKeyframes is not a function
 FAIL Equivalent property indexed and sequenced keyframes: same composite applied to all keyframes (intermediate value).getKeyframes is not a function
 FAIL Custom iterator with basic keyframes. effect.getKeyframes is not a function
 FAIL easing and offset are ignored on iterable objects. effect.getKeyframes is not a function
 FAIL Custom iterator with multiple properties specified. effect.getKeyframes is not a function
 FAIL Custom iterator with offset specified. effect.getKeyframes is not a function
-FAIL Custom iterator with non object keyframe should throw. assert_throws: function "function () {
-    new KeyframeEffect(null, createIterable([
-      {done: false, value: {left: '100px'}},
-      {done: false, value: 1234},
-      {done: false, value: {left: '200px'}},
-      {done: true},
-    ]));
-  }" did not throw
+PASS Custom iterator with non object keyframe should throw. 
 FAIL Custom iterator with value list in keyframe should give bizarre string representation of list. effect.getKeyframes is not a function
 FAIL Only enumerable properties on keyframes are considered anim.effect.getKeyframes is not a function
 FAIL Only properties defined directly on keyframes are considered anim.effect.getKeyframes is not a function
 FAIL Only enumerable properties on property indexed keyframes are considered anim.effect.getKeyframes is not a function
 FAIL Only properties defined directly on property indexed keyframes are considered anim.effect.getKeyframes is not a function
 Harness: the test ran to completion.