GitLab

Changes the location of the RGB→Grayscale conversion of the
CopyFromSurface() result SkBitmap to be in
NavigationEntryScreenshotManager, as it is the only use case. This
unblocks a massive clean-up effort for bug 759310.

For reference, the following was the code that was doing the conversion
before (and is a part of a major chunk of code that we want to delete):
https://cs.chromium.org/chromium/src/content/browser/compositor/surface_utils.cc?rcl=2fe7073e23caa42cbd01575ab206ba8928ccd645&l=146

Bug: 759310
Change-Id: I2687e69b284d5c24ead10b05b49f678cf8375651
Reviewed-on: https://chromium-review.googlesource.com/919603
Commit-Queue: Yuri Wiitala <miu@chromium.org>
Reviewed-by: Nick Carter <nick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#536929}