Use correct gradient calculation for rotated distance fields.

src/gpu/effects/GrDistanceFieldGeoProc.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrDistanceFieldGeoProc_DEFINED
 #define GrDistanceFieldGeoProc_DEFINED
 
 #include "GrProcessor.h"
 #include "GrGeometryProcessor.h"
 
 class GrGLDistanceFieldA8TextGeoProc;
 class GrGLDistanceFieldPathGeoProc;
 class GrGLDistanceFieldLCDTextGeoProc;
 class GrInvariantOutput;
 
 enum GrDistanceFieldEffectFlags {
     kSimilarity_DistanceFieldEffectFlag = 0x01,   // ctm is similarity matrix
-    kRectToRect_DistanceFieldEffectFlag = 0x02,   // ctm maps rects to rects
+    kScaleOnly_DistanceFieldEffectFlag  = 0x02,   // ctm has only scale and translate
     kUseLCD_DistanceFieldEffectFlag     = 0x04,   // use lcd text
     kBGR_DistanceFieldEffectFlag        = 0x08,   // lcd display has bgr order
     kPortrait_DistanceFieldEffectFlag   = 0x10,   // lcd display is in portrait mode (not used yet)
 
     kInvalid_DistanceFieldEffectFlag    = 0x80,   // invalid state (for initialization)
     
     kUniformScale_DistanceFieldEffectMask = kSimilarity_DistanceFieldEffectFlag |
-                                            kRectToRect_DistanceFieldEffectFlag,
+                                            kScaleOnly_DistanceFieldEffectFlag,
     // The subset of the flags relevant to GrDistanceFieldA8TextGeoProc
-    kNonLCD_DistanceFieldEffectMask       = kSimilarity_DistanceFieldEffectFlag,
+    kNonLCD_DistanceFieldEffectMask       = kSimilarity_DistanceFieldEffectFlag |
+                                            kScaleOnly_DistanceFieldEffectFlag,
     // The subset of the flags relevant to GrDistanceFieldLCDTextGeoProc
     kLCD_DistanceFieldEffectMask          = kSimilarity_DistanceFieldEffectFlag |
-                                            kRectToRect_DistanceFieldEffectFlag |
+                                            kScaleOnly_DistanceFieldEffectFlag |
                                             kUseLCD_DistanceFieldEffectFlag |
                                             kBGR_DistanceFieldEffectFlag,
 };
 
 /**
  * The output color of this effect is a modulation of the input color and a sample from a
  * distance field texture (using a smoothed step function near 0.5).
  * It allows explicit specification of the filtering and wrap modes (GrTextureParams). The input
  * coords are a custom attribute. Gamma correction is handled via a texture LUT.
  */
@@ skipping 176 matching lines @@
     const Attribute* fInColor;
     const Attribute* fInTextureCoords;
     bool             fUsesLocalCoords;
 
     GR_DECLARE_GEOMETRY_PROCESSOR_TEST;
 
     typedef GrGeometryProcessor INHERITED;
 };
 
 #endif