Fix bounds computation for non-aa hairlines when snapping to pixel centers

src/gpu/batches/GrNonAAStrokeRectBatch.cpp

Index: src/gpu/batches/GrNonAAStrokeRectBatch.cpp
diff --git a/src/gpu/batches/GrNonAAStrokeRectBatch.cpp b/src/gpu/batches/GrNonAAStrokeRectBatch.cpp
index a38760c362ea14b8f04796bf07f9b5fe8c8972f2..61335523f7a87180ac104d6241c2480f25a020bd 100644
--- a/src/gpu/batches/GrNonAAStrokeRectBatch.cpp
+++ b/src/gpu/batches/GrNonAAStrokeRectBatch.cpp
@@ -100,6 +100,16 @@ private:
 
         // If our caller snaps to pixel centers then we have to round out the bounds
         if (snapToPixelCenters) {
+            // We want to be consistent with how we snap non-aa lines. To match what we do in
+            // GrGLSLVertexShaderBuilder, we first floor all the vertex values and then add half a
+            // pixel to force us to pixel centers.
+            bounds->set(SkScalarFloorToScalar(bounds->fLeft),
+                        SkScalarFloorToScalar(bounds->fTop),
+                        SkScalarFloorToScalar(bounds->fRight),
+                        SkScalarFloorToScalar(bounds->fBottom));
+            bounds->offset(0.5f, 0.5f);
+
+            // Round out the bounds to integer values
             bounds->roundOut();

[bsalomon, 2016/07/07 14:19:06]

Do we need this round out? If the rect is rendered at pixel centers the bounds
be at half integers?

         }
     }