Make SkBlurImageFilter capable of cropping during blur (raster path)

SkBlurImageFilter can currently only process a source image
which is larger than or equal to the destination rect. If
the source image (or crop rect) is smaller, it is padded
out to dest size with transparent black via the 6-param
version of applyCropRect().

Fixing this requires modifying all the flavours of RGBA
box_blur() to accept a src crop rect.

BUG=skia:4502, skia:4526
CQ_EXTRA_TRYBOTS=client.skia.android:Test-Android-GCC-Nexus5-CPU-NEON-Arm7-Release-Trybot;client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot

Review URL: https://codereview.chromium.org/1415653003
3 files changed