[Android] Replace crunched image with source code image

The resources in original xwalk_core_library are not valid 9-patch resource
and can't be used for Android studio/Maven. Have to use the resource in the
Chromium source.

BUG=
I mean simplify the loop by merge
```
for f in files;
  if f == filename:
```
into
```
if filename in files:
```