Use threshold of 1 texture coord value per pixel w/ nearest neighbor.

src/gpu/GrCoordTransform.cpp

Index: src/gpu/GrCoordTransform.cpp
diff --git a/src/gpu/GrCoordTransform.cpp b/src/gpu/GrCoordTransform.cpp
index 5bb36fcf76a6fbf8f908398efcf8890a03179b17..a08d454badbfb912d80feb01cda53120ef3dc522 100644
--- a/src/gpu/GrCoordTransform.cpp
+++ b/src/gpu/GrCoordTransform.cpp
@@ -10,7 +10,8 @@
 #include "GrDrawTargetCaps.h"
 #include "GrGpu.h"
 
-void GrCoordTransform::reset(GrCoordSet sourceCoords, const SkMatrix& m, const GrTexture* texture) {
+void GrCoordTransform::reset(GrCoordSet sourceCoords, const SkMatrix& m, const GrTexture* texture,
+                             GrTextureParams::FilterMode filter) {
     SkASSERT(texture);
     SkASSERT(!fInProcessor);
 
@@ -20,8 +21,10 @@ void GrCoordTransform::reset(GrCoordSet sourceCoords, const SkMatrix& m, const G
 
     // Always start at kDefault. Then if precisions differ we see if the precision needs to be
     // increased. Our rule is that we want at least 4 subpixel values in the representation for
-    // coords between 0 to 1. Note that this still might not be enough when drawing with repeat
-    // or mirror-repeat modes but that case can be arbitrarily bad. 
+    // coords between 0 to 1 when bi- or tri-lerping and 1 value when nearest filtering. Note that
+    // this still might not be enough when drawing with repeat or mirror-repeat modes but that case
+    // can be arbitrarily bad.
+    int subPixelThresh = filter > GrTextureParams::kNone_FilterMode ? 4 : 1;
     fPrecision = kDefault_GrSLPrecision;
     if (texture->getContext()) {
         const GrDrawTargetCaps* caps = texture->getContext()->getGpu()->caps();
@@ -33,7 +36,7 @@ void GrCoordTransform::reset(GrCoordSet sourceCoords, const SkMatrix& m, const G
                 SkASSERT(info->supported());
                 // Make sure there is at least 2 bits of subpixel precision in the range of
                 // texture coords from 0.5 to 1.0.
-                if ((2 << info->fBits) / maxD > 4) {
+                if ((2 << info->fBits) / maxD > subPixelThresh) {
                     break;
                 }
                 if (kHigh_GrSLPrecision == fPrecision) {