Bilinear optimization for 1D convolution.

Splits GrGLConvolutionEffect into GrGLBilerpConvolutionEffect and
GrGLBoundedConvolutionEffect. When doing a non-bounded convolution we now
always use the GrGLBilerpConvolutionEffect which uses bilinear filtering to
perform half as many samples in the texture.

BUG=skia:3986

Review URL: https://codereview.chromium.org/1216623003
2 files changed