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

src/core/SkColorSpace.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkColorSpace.h"
 #include "SkColorSpace_Base.h"
 #include "SkEndian.h"
 #include "SkOnce.h"
 
 static bool color_space_almost_equal(float a, float b) {
     return SkTAbs(a - b) < 0.01f;
 }
 
 //////////////////////////////////////////////////////////////////////////////////////////////////
 
 SkColorSpace::SkColorSpace(GammaNamed gammaNamed, const SkMatrix44& toXYZD50, Named named)
-    : fGammaNamed(kNonStandard_GammaNamed)
+    : fGammaNamed(gammaNamed)
     , fToXYZD50(toXYZD50)
     , fNamed(named)
 {}
 
 SkColorSpace_Base::SkColorSpace_Base(sk_sp<SkGammas> gammas, const SkMatrix44& toXYZD50,
                                      Named named, sk_sp<SkData> profileData)
     : INHERITED(kNonStandard_GammaNamed, toXYZD50, named)
     , fGammas(std::move(gammas))
     , fProfileData(std::move(profileData))
 {}
@@ skipping 1061 matching lines @@
     ptr32[4] = SkEndian_SwapBE32(0x000116cc);
     ptr += kTAG_XYZ_Bytes;
 
     // Write copyright tag
     memcpy(ptr, gEmptyTextTag, sizeof(gEmptyTextTag));
 
     // TODO (msarett): Should we try to hold onto the data so we can return immediately if
     //                 the client calls again?
     return SkData::MakeFromMalloc(profile.release(), kICCProfileSize);
 }