Approximate common gamma tables as single values

tests/ColorSpaceTest.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 "Resources.h"
 #include "SkCodec.h"
 #include "SkColorSpace.h"
@@ skipping 56 matching lines @@
     SkAutoTDelete<SkCodec> codec(SkCodec::NewFromStream(stream.release()));
     REPORTER_ASSERT(r, nullptr != codec);
 
 #if (PNG_LIBPNG_VER_MAJOR > 1) || (PNG_LIBPNG_VER_MAJOR == 1 && PNG_LIBPNG_VER_MINOR >= 6)
     SkColorSpace* colorSpace = codec->getColorSpace();
     REPORTER_ASSERT(r, nullptr != colorSpace);
 
     const float red[] = { 0.436066f, 0.222488f, 0.013916f };
     const float green[] = { 0.385147f, 0.716873f, 0.0970764f };
     const float blue[] = { 0.143066f, 0.0606079f, 0.714096f };
-    const float gamma[] = { 0, 0, 0 };  // table-based gamma returns 0 from this its float-getter
+    const float gamma[] = { 2.2f, 2.2f, 2.2f };
     test_space(r, colorSpace, red, green, blue, gamma);
 #endif
 }
 
 DEF_TEST(ColorSpaceParseJpegICCProfile, r) {
     SkAutoTDelete<SkStream> stream(resource("icc-v2-gbr.jpg"));
     REPORTER_ASSERT(r, nullptr != stream);
     if (!stream) {
         return;
     }
@@ skipping 24 matching lines @@
     sk_sp<SkColorSpace> rgbColorSpace = SkColorSpace::NewRGB(
             SkColorSpace::SkGammas(2.2f, 2.2f, 2.2f), srgbToxyzD50);
     REPORTER_ASSERT(r, namedColorSpace == namedColorSpace);
 
     // Change a single value from the sRGB matrix
     srgbToxyzD50.set(2, 2, 0.5f);
     sk_sp<SkColorSpace> strangeColorSpace = SkColorSpace::NewRGB(
             SkColorSpace::SkGammas(2.2f, 2.2f, 2.2f), srgbToxyzD50);
     REPORTER_ASSERT(r, strangeColorSpace != namedColorSpace);
 }