Enable sRGB on iOS, make sRGB decode support optional

src/gpu/gl/GrGLCaps.cpp

Index: src/gpu/gl/GrGLCaps.cpp
diff --git a/src/gpu/gl/GrGLCaps.cpp b/src/gpu/gl/GrGLCaps.cpp
index ec0f6288b4b550899650208d1a64a806bacfb5b8..bb36ef74855790509f887ee1ff3f76d42032240d 100644
--- a/src/gpu/gl/GrGLCaps.cpp
+++ b/src/gpu/gl/GrGLCaps.cpp
@@ -51,6 +51,8 @@ GrGLCaps::GrGLCaps(const GrContextOptions& contextOptions,
     fMipMapLevelAndLodControlSupport = false;
     fRGBAToBGRAReadbackConversionsAreSlow = false;
     fDoManualMipmapping = false;
+    fSRGBDecodeSupport = false;
+    fRequireDecodeForSRGB = true;
 
     fBlitFramebufferFlags = kNoSupport_BlitFramebufferFlag;
 
@@ -607,6 +609,9 @@ void GrGLCaps::init(const GrContextOptions& contextOptions,
         fDoManualMipmapping = true;
     }
 
+    fSRGBDecodeSupport = ctxInfo.hasExtension("GL_EXT_texture_sRGB_decode");
+    fRequireDecodeForSRGB = contextOptions.fRequireDecodeForSRGB;
+
     // Requires fTextureRedSupport, fTextureSwizzleSupport, msaa support, ES compatibility have
     // already been detected.
     this->initConfigTable(ctxInfo, gli, shaderCaps);
@@ -1575,17 +1580,16 @@ void GrGLCaps::initConfigTable(const GrGLContextInfo& ctxInfo, const GrGLInterfa
             fSRGBWriteControl = true;
         }
     } else {
-        // See https://bug.skia.org/4148 for PowerVR issue.
-        fSRGBSupport = kPowerVRRogue_GrGLRenderer != ctxInfo.renderer() &&
-            (ctxInfo.version() >= GR_GL_VER(3,0) || ctxInfo.hasExtension("GL_EXT_sRGB"));
+        fSRGBSupport = ctxInfo.version() >= GR_GL_VER(3,0) || ctxInfo.hasExtension("GL_EXT_sRGB");
         // ES through 3.1 requires EXT_srgb_write_control to support toggling
         // sRGB writing for destinations.
         // See https://bug.skia.org/5329 for Adreno4xx issue.
         fSRGBWriteControl = kAdreno4xx_GrGLRenderer != ctxInfo.renderer() &&
             ctxInfo.hasExtension("GL_EXT_sRGB_write_control");
     }
-    if (!ctxInfo.hasExtension("GL_EXT_texture_sRGB_decode")) {
-        // To support "legacy" L32 mode, we require the ability to turn off sRGB decode:
+    if (fRequireDecodeForSRGB && !fSRGBDecodeSupport) {

[bsalomon, 2016/11/30 17:00:21]

Should we just pass the options here rather than having this fRequire member?

+        // To support "legacy" L32 mode, we require the ability to turn off sRGB decode. Clients
+        // can opt-out of that requirement, if they intend to always do linear blending.
         fSRGBSupport = false;
     }
     fConfigTable[kSRGBA_8888_GrPixelConfig].fFormats.fBaseInternalFormat = GR_GL_SRGB_ALPHA;