Only unbind a Graphics2D on destruction when we're actually bound.

Previously if you made a new Graphics2D, bound it, and deleted the previous one, the first one would blindly unbind the current graphics 2D context in its destructor, which leaves you with a blank page.

BUG=164302

Review URL: https://codereview.chromium.org/11571016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@173181 0039d316-1c4b-4281-b951-d872f2087c98
2 files changed