Fix BGRA/RGBA readback conversions on mac

src/gpu/gl/GrGLCaps.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef GrGLCaps_DEFINED
 #define GrGLCaps_DEFINED
@@ skipping 333 matching lines @@
 
     bool mipMapLevelAndLodControlSupport() const { return fMipMapLevelAndLodControlSupport; }
 
     /**
      * Returns a string containing the caps info.
      */
     SkString dump() const override;
 
     bool rgba8888PixelsOpsAreSlow() const { return fRGBA8888PixelsOpsAreSlow; }
     bool partialFBOReadIsSlow() const { return fPartialFBOReadIsSlow; }
+    bool rgbaToBgraReadbackConversionsAreSlow() const {
+        return fRGBAToBGRAReadbackConversionsAreSlow;
+    }
 
     const GrGLSLCaps* glslCaps() const { return reinterpret_cast<GrGLSLCaps*>(fShaderCaps.get()); }
 
 private:
     enum ExternalFormatUsage {
         kTexImage_ExternalFormatUsage,
         kOther_ExternalFormatUsage,
 
         kLast_ExternalFormatUsage = kOther_ExternalFormatUsage
     };
@@ skipping 50 matching lines @@
     bool fIsCoreProfile : 1;
     bool fBindFragDataLocationSupport : 1;
     bool fSRGBWriteControl : 1;
     bool fRGBA8888PixelsOpsAreSlow : 1;
     bool fPartialFBOReadIsSlow : 1;
     bool fBindUniformLocationSupport : 1;
     bool fExternalTextureSupport : 1;
     bool fRectangleTextureSupport : 1;
     bool fTextureSwizzleSupport : 1;
     bool fMipMapLevelAndLodControlSupport : 1;
+    bool fRGBAToBGRAReadbackConversionsAreSlow : 1;
 
     BlitFramebufferSupport fBlitFramebufferSupport;
 
     /** Number type of the components (with out considering number of bits.) */
     enum FormatType {
         kNormalizedFixedPoint_FormatType,
         kFloat_FormatType,
     };
 
     struct ReadPixelsFormat {
@@ skipping 58 matching lines @@
 
         GrSwizzle fSwizzle;
     };
 
     ConfigInfo fConfigTable[kGrPixelConfigCnt];
 
     typedef GrCaps INHERITED;
 };
 
 #endif