add MakeS32 helper to SkImageInfo, fix named-gamma constructor bug

include/core/SkImageInfo.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkImageInfo_DEFINED
 #define SkImageInfo_DEFINED
 
@@ skipping 205 matching lines @@
     }
 
     /**
      *  Sets colortype to the native ARGB32 type, and the alphatype to premul.
      */
     static SkImageInfo MakeN32Premul(const SkISize& size,
                                      SkColorProfileType pt = kLinear_SkColorProfileType) {
         return MakeN32Premul(size.width(), size.height(), pt);
     }
 
+    /**
+     *  Create an ImageInfo marked as SRGB with N32 swizzle.
+     */
+    static SkImageInfo MakeS32(int width, int height, SkAlphaType at);
+
     static SkImageInfo MakeA8(int width, int height) {
         return SkImageInfo(width, height, kAlpha_8_SkColorType, kPremul_SkAlphaType,
                            kLinear_SkColorProfileType, nullptr);
     }
 
     static SkImageInfo MakeUnknown(int width, int height) {
         return SkImageInfo(width, height, kUnknown_SkColorType, kUnknown_SkAlphaType,
                            kLinear_SkColorProfileType, nullptr);
     }
 
@@ skipping 125 matching lines @@
 
 static inline bool SkColorAndProfileAreGammaCorrect(SkColorType ct, SkColorProfileType pt) {
     return kSRGB_SkColorProfileType == pt || kRGBA_F16_SkColorType == ct;
 }
 
 static inline bool SkImageInfoIsGammaCorrect(const SkImageInfo& info) {
     return SkColorAndProfileAreGammaCorrect(info.colorType(), info.profileType());
 }
 
 #endif