Only use fake gamma with linear devices.

include/core/SkPaint.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkPaint_DEFINED
 #define SkPaint_DEFINED
 
@@ skipping 1054 matching lines @@
         } fBitfields;
         uint32_t fBitfieldsUInt;
     };
 
     SkDrawCacheProc    getDrawCacheProc() const;
     SkMeasureCacheProc getMeasureCacheProc(bool needFullMetrics) const;
 
     SkScalar measure_text(SkGlyphCache*, const char* text, size_t length,
                           int* count, SkRect* bounds) const;
 
+    enum class FakeGamma {
+        Off = 0, On
+    };
+
     /*
      * Allocs an SkDescriptor on the heap and return it to the caller as a refcnted
      * SkData.  Caller is responsible for managing the lifetime of this object.
      */
     void getScalerContextDescriptor(SkAutoDescriptor*, const SkSurfaceProps& surfaceProps,
-                                    const SkMatrix*, bool ignoreGamma) const;
+                                    FakeGamma fakeGamma, const SkMatrix*) const;
 
-    SkGlyphCache* detachCache(const SkSurfaceProps* surfaceProps, const SkMatrix*,
-                              bool ignoreGamma) const;
+    SkGlyphCache* detachCache(const SkSurfaceProps* surfaceProps, FakeGamma fakeGamma,
+                              const SkMatrix*) const;
 
-    void descriptorProc(const SkSurfaceProps* surfaceProps, const SkMatrix* deviceMatrix,
+    void descriptorProc(const SkSurfaceProps* surfaceProps, FakeGamma fakeGamma,
+                        const SkMatrix* deviceMatrix,
                         void (*proc)(SkTypeface*, const SkDescriptor*, void*),
-                        void* context, bool ignoreGamma) const;
+                        void* context) const;
 
     /*
      * The luminance color is used to determine which Gamma Canonical color to map to.  This is
      * really only used by backends which want to cache glyph masks, and need some way to know if
      * they need to generate new masks based off a given color.
      */
     SkColor computeLuminanceColor() const;
 
     enum {
         /*  This is the size we use when we ask for a glyph's path. We then
@@ skipping 43 matching lines @@
     friend class GrStencilAndCoverTextContext;
     friend class GrPathRendering;
     friend class GrTextUtils;
     friend class GrGLPathRendering;
     friend class SkScalerContext;
     friend class SkTextBaseIter;
     friend class SkCanonicalizePaint;
 };
 
 #endif