Manually generated sRGB mipmaps.

src/gpu/gl/GrGLGpu.h

Index: src/gpu/gl/GrGLGpu.h
diff --git a/src/gpu/gl/GrGLGpu.h b/src/gpu/gl/GrGLGpu.h
index 0b2198a8342ae69d66fb865140e1df56e94c383f..9640d3331582b3e960c0b86d138caa7faaea242a 100644
--- a/src/gpu/gl/GrGLGpu.h
+++ b/src/gpu/gl/GrGLGpu.h
@@ -62,6 +62,8 @@ public:
 
     void bindTexelBuffer(int unitIdx, intptr_t offsetInBytes, GrPixelConfig, GrGLBuffer*);
 
+    void generateMipmaps(const GrTextureParams& params, bool allowSRGBInputs, GrGLTexture* texture);
+
     bool onGetReadPixelsInfo(GrSurface* srcSurface, int readWidth, int readHeight, size_t rowBytes,
                              GrPixelConfig readConfig, DrawPreference*,
                              ReadPixelTempDrawInfo*) override;
@@ -237,6 +239,7 @@ private:
                                       GrSurface* src,
                                       const SkIRect& srcRect,
                                       const SkIPoint& dstPoint);
+    bool generateMipmap(GrGLTexture* texture, bool gammaCorrect);
 
     void stampPLSSetupRect(const SkRect& bounds);
 
@@ -319,6 +322,8 @@ private:
 
     void flushMinSampleShading(float minSampleShading);
 
+    void flushFramebufferSRGB(bool enable);
+
     // helper for onCreateTexture and writeTexturePixels
     enum UploadType {
         kNewTexture_UploadType,    // we are creating a new texture