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Now that the image resources that blink depends on are in the blink
repository, we depend on the blink resources directly, delete the ones
in the chrome tree, and use these resources in the html_viewer.

[This reland also contains a fix to the generate_blink_resource_map.py
file so that its generated code uses unsigned chars, which should
hopefully fix the Win8 gn bot.]

BUG=467176
First Review URL: https://codereview.chromium.org/1033733004

Review URL: https://codereview.chromium.org/1038723002

Cr-Commit-Position: refs/heads/master@{#322427}