add legacy bitmap filter flag for skia
add legacy bitmap filter flag for skia

An upcoming Skia CL improves the performance for filtered bitmaps.
Rearranging some expressions that compute the filter kernel causes
0.01% - 0.02% of the pixels to differ by (1,1,1). This changes around
240 layout test results.

Suppress the Skia CL with this guard until the tests can be
rebaselined.

R=fmalita@chromium.org
BUG=skia:2261

Review URL: https://codereview.chromium.org/1583533002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#368932}

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