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This adds the missing conditions to the chrome/common GN build file (previously
only the basic files were there). Some refactoring of the GYP file to make this
possible.

Renames the enable_printing flag to printing_mode since this is an integer
tri-state.

Minor improvements to chrome/renderer

R=jamesr@chromium.org

Review URL: https://codereview.chromium.org/400243003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284508 0039d316-1c4b-4281-b951-d872f2087c98