Revert of Enable sRGB on iOS, make sRGB decode support optional

tests/SRGBMipMapTest.cpp

Index: tests/SRGBMipMapTest.cpp
diff --git a/tests/SRGBMipMapTest.cpp b/tests/SRGBMipMapTest.cpp
index 88f08d43d73e77a214f55bfd775608ef76f63f1a..a875c5c71033afcba2d57daf008d1eaf63932fbf 100644
--- a/tests/SRGBMipMapTest.cpp
+++ b/tests/SRGBMipMapTest.cpp
@@ -10,7 +10,6 @@
 #include "GrCaps.h"
 #include "GrContext.h"
 #include "GrRenderTargetContext.h"
-#include "gl/GrGLGpu.h"
 #include "SkCanvas.h"
 #include "SkSurface.h"
 
@@ -143,18 +142,8 @@
     // 2) Draw texture to L32 surface (should generate/use linear mips)
     paint.setGammaCorrect(false);
     l32RenderTargetContext->drawRect(noClip, paint, SkMatrix::I(), rect);
-
-    // Right now, this test only runs on GL (because Vulkan doesn't support legacy mip-mapping
-    // skbug.com/5048). On GL, we may not have sRGB decode support. In that case, rendering sRGB
-    // textures to a legacy surface produces nonsense, so this part of the test is meaningless.
-    //
-    // TODO: Once Vulkan supports legacy mip-mapping, we can promote this to GrCaps. Right now,
-    // Vulkan has most of the functionality, but not the mip-mapping part that's being tested here.
-    GrGLGpu* glGpu = static_cast<GrGLGpu*>(context->getGpu());
-    if (glGpu->glCaps().srgbDecodeDisableSupport()) {
-        read_and_check_pixels(reporter, l32RenderTargetContext->asTexture().get(), expectedLinear,
-                              error, "re-render as linear");
-    }
+    read_and_check_pixels(reporter, l32RenderTargetContext->asTexture().get(), expectedLinear,
+                          error, "re-render as linear");
 
     // 3) Go back to sRGB
     paint.setGammaCorrect(true);