Avoid "Member not found exception" in IE10

'change' custom events raise "Member not found" in <= IE10. To
circumvent this, the SyntheticEvent class now checks for "typeof
event.cancelBubble !== 'unknown'". This eliminates this exception and
maintains the expected bubbling functionality.

Addresses facebook#7320.

src/renderers/dom/client/syntheticEvents/SyntheticEvent.js

@@ -135,9 +135,13 @@ Object.assign(SyntheticEvent.prototype, {
 
     if (event.stopPropagation) {
       event.stopPropagation();
-    } else {
+    } else if (typeof event.cancelBubble !== 'unknown') { // eslint-disable-line valid-typeof
+      // <= IE10 throws a "Member not found" error if the cancelBubble
+      // attribute is accessed from an onChange event. A typeof check of "unknown"
+      // circumvents this issue.
       event.cancelBubble = true;
     }
+
     this.isPropagationStopped = emptyFunction.thatReturnsTrue;
   },