Removed navigator.canShare.

Resolves #5.

Author: mgiuca

docs/explainer.md

@@ -51,11 +51,13 @@ shareButton.addEventListener('click', () => {
 });
 ```
 
-You can also test in advance whether there are any installed apps or services
-that support sharing (so you can not show the button if you know it won't work):
+Developers should be aware that not all user agents will provide
+`navigator.share` (sometimes intentionally; for instance, a browser may not
+provide it when running on a platform that has no share support). Feature
+detection can be used to avoid showing a non-functioning button on a web page:
 
 ```js
-if (!navigator.canShare())
+if (navigator.share === undefined)
   shareButton.hidden = true;
 ```
 

docs/interface.md

@@ -66,28 +66,8 @@ modes, but not learn the identity of the chosen application):
 * The data could not be delivered to the target app (e.g., the chosen app could
   not be launched), or the target app explicitly rejected the share event.
 
-## navigator.canShare
-
-`navigator` also provides a method for determining whether there are any
-applications that can handle sharing:
-
-```WebIDL
-partial interface Navigator {
-  boolean canShare();
-};
-```
-
-Returns `true` if there are one or more applications that could handle a share
-event (i.e., if `share` was called, would any applications be presented to the
-user?). May give false positives, but not false negatives (on some systems, it
-may not be possible to determine in advance whether any native applications
-support sharing, in which case `canShare` should return `true`; `false` means
-that `share` will definitely fail). This can be used by websites to hide or
-disable the sharing UI, to avoid presenting a button that just fails when users
-press it.
-
-**TODO(mgiuca)**: This may have to be asynchronous, so that the implementation
-can query the file system without blocking.
+The `navigator.share` method should be `undefined` if the user agent does not
+support any share targets.
 
 ## Share handlers