Never allow dither for non-legacy (sRGB or F16) targets.

src/gpu/SkGr.cpp

 /*
  * Copyright 2010 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkGr.h"
 #include "SkGrPriv.h"
@@ skipping 637 matching lines @@
 
     // When the xfermode is null on the SkPaint (meaning kSrcOver) we need the XPFactory field on
     // the GrPaint to also be null (also kSrcOver).
     SkASSERT(!grPaint->getXPFactory());
     SkXfermode* xfermode = skPaint.getXfermode();
     if (xfermode) {
         grPaint->setXPFactory(xfermode->asXPFactory());
     }
 
 #ifndef SK_IGNORE_GPU_DITHER
-    if (skPaint.isDither() && grPaint->numColorFragmentProcessors() > 0) {
+    if (skPaint.isDither() && grPaint->numColorFragmentProcessors() > 0 && !allowSRGBInputs) {

[jvanverth1, 2016/06/30 20:21:37]

Does allowSRGBInputs include F16? If so, that seems a little confusing.

         grPaint->addColorFragmentProcessor(GrDitherEffect::Make());
     }
 #endif
     return true;
 }
 
 bool SkPaintToGrPaint(GrContext* context, const SkPaint& skPaint, const SkMatrix& viewM,
                       bool allowSRGBInputs, GrPaint* grPaint) {
     return skpaint_to_grpaint_impl(context, skPaint, viewM, nullptr, nullptr, false,
                                    allowSRGBInputs, grPaint);
@@ skipping 129 matching lines @@
             SkErrorInternals::SetError( kInvalidPaint_SkError,
                                         "Sorry, I don't understand the filtering "
                                         "mode you asked for.  Falling back to "
                                         "MIPMaps.");
             textureFilterMode = GrTextureParams::kMipMap_FilterMode;
             break;
 
     }
     return textureFilterMode;
 }