Convert URI scheme to lower case before checking if it is a file.

This fixes an edge case where a "File://" style URI could be passed in
but not pass this check, even though the underlying framework recognizes
this as a legitimate file.

Bug: 197328178
Test: See repro steps on http://b/197328178, was no longer able to
repro.

Change-Id: Id837744a79d1aca91b41d24207dc9b98f2b5b5e9
(cherry picked from commit 9607c95e71)

src/com/android/messaging/util/UriUtil.java

@@ -94,8 +94,12 @@ public class UriUtil {
         return TextUtils.equals(scheme, ContentResolver.SCHEME_ANDROID_RESOURCE);
     }
 
+    /** Returns whether the given Uri is a file. */
     public static boolean isFileUri(final Uri uri) {
-        return uri != null && TextUtils.equals(uri.getScheme(), ContentResolver.SCHEME_FILE);
+        return uri != null &&
+                uri.getScheme() != null &&
+                TextUtils.equals(uri.getScheme().toLowerCase(),
+                        ContentResolver.SCHEME_FILE);
     }
 
     /**