Cherrypick: [Android] Use Blink UTF8<->UTF16 strings conversion in Gin Java Bridge

Original description:

> This patch is mainly for merging into M37. In trunk, we should fix
> base:: conversion routines instead.
> Blink UTF conversion routines are considerably faster than the ones
> from base::, especially on strings that only contain Latin-1 characters,
> so use them instead. This gives a 9% speed gain on Cordova's "exec"
> benchmark.
> BUG=391492
> Review URL:
> git-svn-id: svn:// 0039d316-1c4b-4281-b951-d872f2087c98

Bug: 10146351

Change-Id: I22ec2f7aea742f403763801526a15239b5580b1e
2 files changed