Fix rounding error with tiled bitmap draws

We were snapping the top-left of the destination rectangle to integers,
but using the original (fractional) size. This led to us losing rows or
columns of pixels at the first tile boundary.

Also added a GM that demonstrates the bug (now renders correctly).

BUG=skia:

Change-Id: I50629dab9dd90fedad2c7e3393a1b1d1c7a8d45e
Reviewed-on: https://skia-review.googlesource.com/8102
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/gn/gm.gni b/gn/gm.gni
index 38e50b57ec..409376c19d 100644
--- a/gn/gm.gni
+++ b/gn/gm.gni
@@ -36,6 +36,7 @@ gm_sources = [
   "$_gm/bitmaprect.cpp",
   "$_gm/bitmaprecttest.cpp",
   "$_gm/bitmapshader.cpp",
+  "$_gm/bitmaptiled.cpp",
   "$_gm/bleed.cpp",
   "$_gm/blend.cpp",
   "$_gm/blurcircles.cpp",