Centralize decision about whether to do bicubic filtering, and fallbacks to mip, bilerp, or nearest

src/gpu/effects/GrBicubicEffect.h

Index: src/gpu/effects/GrBicubicEffect.h
diff --git a/src/gpu/effects/GrBicubicEffect.h b/src/gpu/effects/GrBicubicEffect.h
index cc8b1208634d76a2627f6d8c4f5946a6bb2ff7b8..7949c2e9728ae7198feead0fd2f377b66f9974b8 100644
--- a/src/gpu/effects/GrBicubicEffect.h
+++ b/src/gpu/effects/GrBicubicEffect.h
@@ -78,6 +78,15 @@ public:
         return CreateEffectRef(effect);
     }
 
+    /**

[robertphillips, 2014/05/20 15:34:50]

The return value discussion doesn't seem right.
Maybe:
// Returns false if the filterMode has been changed; true otherwise. ?

[bsalomon, 2014/05/20 16:13:06]

Done.

+     * Determines whether the bicubic effect should be used based on the transformation from the
+     * local coords to the device. filterMode will be set to kNearest if true is returned (as no
+     * built-in filtering should be used with the bicubic effect) or the fallback filterMode that
+     * should be used if false is returned.
+     */
+    static bool ShouldUseBicubic(const SkMatrix& localCoordsToDevice,
+                                 GrTextureParams::FilterMode* filterMode);
+
 private:
     GrBicubicEffect(GrTexture*, const SkScalar coefficients[16],
                     const SkMatrix &matrix, const SkShader::TileMode tileModes[2]);