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

src/effects/SkDisplacementMapEffect.cpp

Index: src/effects/SkDisplacementMapEffect.cpp
diff --git a/src/effects/SkDisplacementMapEffect.cpp b/src/effects/SkDisplacementMapEffect.cpp
index e74ca4fe3fbe1a3475cb0975f11965c4688bab92..0f49a991c22e9a0c6c938d0b5409b7fb62042f47 100644
--- a/src/effects/SkDisplacementMapEffect.cpp
+++ b/src/effects/SkDisplacementMapEffect.cpp
@@ -19,6 +19,7 @@
 #include "GrCoordTransform.h"
 #include "GrInvariantOutput.h"
 #include "SkGr.h"
+#include "SkGrPriv.h"
 #include "effects/GrTextureDomain.h"
 #include "glsl/GrGLSLFragmentProcessor.h"
 #include "glsl/GrGLSLFragmentShaderBuilder.h"
@@ -337,7 +338,8 @@ sk_sp<SkSpecialImage> SkDisplacementMapEffect::onFilterImage(SkSpecialImage* sou
 
         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;
         }