Fix some GPU image filter code to preserve precision and color space

src/effects/SkDisplacementMapEffect.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkDisplacementMapEffect.h"
 
 #include "SkBitmap.h"
 #include "SkReadBuffer.h"
 #include "SkSpecialImage.h"
 #include "SkWriteBuffer.h"
 #include "SkUnPreMultiply.h"
 #include "SkColorPriv.h"
 #if SK_SUPPORT_GPU
 #include "GrContext.h"
 #include "GrDrawContext.h"
 #include "GrCoordTransform.h"
 #include "GrInvariantOutput.h"
 #include "SkGr.h"
+#include "SkGrPriv.h"
 #include "effects/GrTextureDomain.h"
 #include "glsl/GrGLSLFragmentProcessor.h"
 #include "glsl/GrGLSLFragmentShaderBuilder.h"
 #include "glsl/GrGLSLProgramDataManager.h"
 #include "glsl/GrGLSLUniformHandler.h"
 #endif
 
 namespace {
 
 #define kChannelSelectorKeyBits 3; // Max value is 4, so 3 bits are required at most
@@ skipping 298 matching lines @@
                                           displTexture.get(),
                                           offsetMatrix,
                                           colorTexture.get(),
                                           SkISize::Make(color->width(), color->height())));
         paint.setPorterDuffXPFactory(SkXfermode::kSrc_Mode);
         SkMatrix matrix;
         matrix.setTranslate(-SkIntToScalar(colorBounds.x()), -SkIntToScalar(colorBounds.y()));
 
         sk_sp<GrDrawContext> drawContext(
             context->makeDrawContext(SkBackingFit::kApprox, bounds.width(), bounds.height(),
-                                     kSkia8888_GrPixelConfig, sk_ref_sp(source->getColorSpace())));
+                                     GrRenderableConfigForColorSpace(source->getColorSpace()),
+                                     sk_ref_sp(source->getColorSpace())));
         if (!drawContext) {
             return nullptr;
         }
 
         drawContext->drawRect(GrNoClip(), paint, matrix, SkRect::Make(colorBounds));
 
         offset->fX = bounds.left();
         offset->fY = bounds.top();
         return SkSpecialImage::MakeFromGpu(SkIRect::MakeWH(bounds.width(), bounds.height()),
                                            kNeedNewImageUniqueID_SpecialImage,
@@ skipping 267 matching lines @@
 void GrGLDisplacementMapEffect::GenKey(const GrProcessor& proc,
                                        const GrGLSLCaps&, GrProcessorKeyBuilder* b) {
     const GrDisplacementMapEffect& displacementMap = proc.cast<GrDisplacementMapEffect>();
 
     uint32_t xKey = displacementMap.xChannelSelector();
     uint32_t yKey = displacementMap.yChannelSelector() << kChannelSelectorKeyBits;
 
     b->add32(xKey | yKey);
 }
 #endif