Finish migrating from googleurl/src/gurl.h to url/gurl.h.

Chromium M31 has wiped out the googleurl directory and merged the googleurl
repository into the Chromium one.

I guess the build bots (and the developers' checkouts) kept src/googleurl/
around for some reason and the build did not fail before, but the canaries,
which start from a fresh checkout every time, were failing:

../../xwalk/runtime/browser/android/net/android_protocol_handler.cc:14:32:fatal error: googleurl/src/gurl.h: No such file or directory
Merge pull request #852 from rakuco/gurl-includes

Finish migrating from googleurl/src/gurl.h to url/gurl.h.