fixing bug in 2D context painted area pixel count computation  TEST=none BUG=none Review URL: http://codereview.chromium.org/1611011
fixing bug in 2D context painted area pixel count computation 
TEST=none
BUG=none
Review URL: http://codereview.chromium.org/1611011

git-svn-id: http://src.chromium.org/svn/trunk/src@44103 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 5034c991223ed0211acd26c8957632edb1598dbb
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser