Remove SK_SUPPORT_LEGACY_ANISOTROPIC_MIPMAPS
Remove SK_SUPPORT_LEGACY_ANISOTROPIC_MIPMAPS

Improves anisotropic mipmap scaling.

TBR=reed@google.com

Review URL: https://codereview.chromium.org/1611413006

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#371153}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk