Decode URL encoding in resource attriute for images

In getFilename(), decode URL encoding and replace the search
for 'File:' with a more standard ./ stripping regex.

The ./ regex came from generateContents) in the CE class;
made that code use getFilename() instead.

Also apply decodeURIComponent() to the result; but protect against
exceptions because it's a useless piece of garbage.

Bug: 65611
Change-Id: I7e81a8dc26d1c636c6571d96f43a394a53490587
Merge "Decode URL encoding in resource attriute for images"