Enable sRGB on iOS, make sRGB decode support optional

src/gpu/gl/GrGLCaps.h

Index: src/gpu/gl/GrGLCaps.h
diff --git a/src/gpu/gl/GrGLCaps.h b/src/gpu/gl/GrGLCaps.h
index 5c7e02874575296540d2a78e56d82b377724a505..deb0889c82088c3d5ac582a7dc501838a94a7f7b 100644
--- a/src/gpu/gl/GrGLCaps.h
+++ b/src/gpu/gl/GrGLCaps.h
@@ -345,6 +345,8 @@ public:
 
     bool doManualMipmapping() const { return fDoManualMipmapping; }
 
+    bool srgbDecodeDisableSupport() const { return fSRGBDecodeDisableSupport; }
+
     /**
      * Returns a string containing the caps info.
      */
@@ -378,7 +380,8 @@ private:
     void initBlendEqationSupport(const GrGLContextInfo&);
     void initStencilFormats(const GrGLContextInfo&);
     // This must be called after initFSAASupport().
-    void initConfigTable(const GrGLContextInfo&, const GrGLInterface*, GrShaderCaps*);
+    void initConfigTable(const GrContextOptions&, const GrGLContextInfo&, const GrGLInterface*,
+                         GrShaderCaps*);
 
     void initShaderPrecisionTable(const GrGLContextInfo&, const GrGLInterface*, GrShaderCaps*);
 
@@ -420,6 +423,7 @@ private:
     bool fMipMapLevelAndLodControlSupport : 1;
     bool fRGBAToBGRAReadbackConversionsAreSlow : 1;
     bool fDoManualMipmapping : 1;
+    bool fSRGBDecodeDisableSupport : 1;
 
     uint32_t fBlitFramebufferFlags;