Enable sRGB on iOS, make sRGB decode support optional

tools/flags/SkCommonFlagsConfig.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkColorSpace_Base.h"
 #include "SkCommonFlagsConfig.h"
 #include "SkImageInfo.h"
@@ skipping 167 matching lines @@
         , fUseDIText(useDIText)
         , fSamples(samples)
         , fColorType(colorType)
         , fColorSpace(std::move(colorSpace)) {
     if (useNVPR) {
         fContextOptions |= ContextOptions::kEnableNVPR;
     }
     if (useInstanced) {
         fContextOptions |= ContextOptions::kUseInstanced;
     }
+    // Subtle logic: If the config has a color space attached, we're going to be rendering to sRGB,
+    // so we need that capability. In addition, to get the widest test coverage, we DO NOT require
+    // that we can disable sRGB decode. (That's for rendering sRGB sources to legacy surfaces).
+    //
+    // If the config doesn't have a color space attached, we're going to be rendering in legacy
+    // mode. In that case, we can't allow a context to be created that has sRGB support without
+    // the ability to disable sRGB decode. Otherwise, all of our sRGB source resources will be
+    // treated as sRGB textures, but we will be unable to prevent the decode, causing them to be
+    // too dark.
     if (fColorSpace) {
         fContextOptions |= ContextOptions::kRequireSRGBSupport;
+    } else {
+        fContextOptions |= ContextOptions::kRequireSRGBDecodeDisableSupport;
     }
 }
 static bool parse_option_int(const SkString& value, int* outInt) {
     if (value.isEmpty()) {
         return false;
     }
     char* endptr = nullptr;
     long intValue = strtol(value.c_str(), &endptr, 10);
     if (*endptr != '\0') {
         return false;
@@ skipping 240 matching lines @@
         if (extendedBackend.equals("gpu")) {
             parsedConfig = parse_command_line_config_gpu(tag, vias, extendedOptions);
         }
 #endif
         if (!parsedConfig) {
             parsedConfig = new SkCommandLineConfig(tag, simpleBackend, vias);
         }
         outResult->emplace_back(parsedConfig);
     }
 }