Have drawBitmapRectToRect devolve to drawBitmap if it can (to avoid creating

Have drawBitmapRectToRect devolve to drawBitmap if it can (to avoid creating
a bitmap-shader, which is slower when the matrix is nearly translate-only).

SK_IGNORE_DRAWBITMAPRECT_AS_DRAWBITMAP will disable this if needed.
Committed: https://code.google.com/p/skia/source/detail?r=7208

[reed1, 2013-01-15 20:51:48]

Before

running bench [640 480]   bitmaprect_FF_filter_trans  8888: cmsecs =   4.66
running bench [640 480] bitmaprect_FF_nofilter_trans  8888: cmsecs =   4.67
running bench [640 480] bitmaprect_FF_filter_identity  8888: cmsecs =   2.15
running bench [640 480] bitmaprect_FF_nofilter_identity  8888: cmsecs =   2.15

After

running bench [640 480]   bitmaprect_FF_filter_trans  8888: cmsecs =   1.54
running bench [640 480] bitmaprect_FF_nofilter_trans  8888: cmsecs =   1.54
running bench [640 480] bitmaprect_FF_filter_identity  8888: cmsecs =   1.51
running bench [640 480] bitmaprect_FF_nofilter_identity  8888: cmsecs =   1.51

[robertphillips, 2013-01-15 20:56:24]

LGTM