Messenger refuses all file:///data/ uris

We've been informed it's possible for an app to create a world
readable hardlink in L in its own /data directory that links to
another apps private data, including Messenger data. The hardlink
bypassed our existing checks. So now we simply refuse all file: uris
in the /data/ directory.
Other apps shouldn't be sending file uris anyway, and we dont know
of any that send file:///data/ uris.

Bug: 28793303
Change-Id: I778bb2bcb9e11185357093c59fc1fa3f6caa26a1

src/com/android/messaging/ui/conversationlist/ShareIntentActivity.java

@@ -159,7 +159,7 @@ public class ShareIntentActivity extends BaseBugleActivity implements
     }
 
     private void addSharedImagePartToDraft(final String contentType, final Uri imageUri) {
-        if (FileUtil.isInPrivateDir(getBaseContext(), imageUri)) {
+        if (FileUtil.isInPrivateDir(imageUri)) {
             Assert.fail("Cannot send private file " + imageUri.toString());
         } else {
             mDraftMessage.addPart(PendingAttachmentData.createPendingAttachmentData(contentType,