Fix org.xwalk.core.internal.xwview.test.loadTest#testContentUrl

Since M37 the test was failing. It was missing to change the declaration
of TestContentProvider the same way we did for the non internal xwalkview.

BUG=XWALK-2172
Merge pull request #2248 from darktears/fix-test

Fix org.xwalk.core.internal.xwview.test.loadTest#testContentUrl