Add check that the CSSValue is a valid type in CSSTransformComponent before casting

third_party/WebKit/LayoutTests/typedcssom/inlinestyle/transform.html

Index: third_party/WebKit/LayoutTests/typedcssom/inlinestyle/transform.html
diff --git a/third_party/WebKit/LayoutTests/typedcssom/inlinestyle/transform.html b/third_party/WebKit/LayoutTests/typedcssom/inlinestyle/transform.html
index 58d05b488eb78f89188c960125c47016e2d7041d..e9bcd92182a4d72593bbadcd32baaa025b824a3c 100644
--- a/third_party/WebKit/LayoutTests/typedcssom/inlinestyle/transform.html
+++ b/third_party/WebKit/LayoutTests/typedcssom/inlinestyle/transform.html
@@ -3,6 +3,7 @@
 <script src="../../resources/testharnessreport.js"></script>
 
 <div id="testElement"></div>
+<div id="crashTest" style="transform:translateY(50px)"></div>
 
 <script>
 
@@ -22,5 +23,8 @@ test(function() {
   assert_equals(testElement.styleMap.get('transform').cssText, 'rotate(30deg)');
 }, "Getting transform works on a regular element.");
 
+test(function() {
+  crashTest.styleMap.entries();
+}, "Unhandled case doesn't crash.");
 
 </script>