Metal: Add Shadow Sampler Grad workaround for AMD

This change allows the direct translator to
use emulated gradient shadow compare functions for
AMD devices, and devices that don't support shadow compare
sampler.

Bug: angleproject:5107
Change-Id: I8cc8dcb6e6982531c2a858782869283e6dc97052
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3232818
Commit-Queue: Kyle Piddington <kpiddington@apple.com>
Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>
Reviewed-by: Kenneth Russell <kbr@chromium.org>

src/libANGLE/renderer/metal/DisplayMtl.mm

@@ -992,8 +992,9 @@ void DisplayMtl::initializeFeatures()
 
     ANGLE_FEATURE_CONDITION((&mFeatures), allowRuntimeSamplerCompareMode,
                             supportsEitherGPUFamily(3, 1));
+    // AMD does not support sample_compare_grad
     ANGLE_FEATURE_CONDITION((&mFeatures), allowSamplerCompareGradient,
-                            supportsEitherGPUFamily(3, 1));
+                            supportsEitherGPUFamily(3, 1) && !isAMD());
     ANGLE_FEATURE_CONDITION((&mFeatures), allowSamplerCompareLod, supportsEitherGPUFamily(3, 1));
 
     // http://anglebug.com/4919

src/tests/deqp_support/deqp_gles3_test_expectations.txt

@@ -558,11 +558,6 @@
 
 /////////// Metal ////////////////
 
-// shadow sampler doesn't support bias & gradient & lod versions
-5107 MAC METAL AMD : dEQP-GLES3.*texturegrad*shadow* = SKIP
-5107 MAC METAL AMD : dEQP-GLES3.*textureprojgrad*shadow* = SKIP
-
-
 // last provoking vertex (for flat shading) is not supported
 5232 MAC METAL : dEQP-GLES3.*flatshading* = FAIL
 5232 MAC METAL AMD : dEQP-GLES3.functional.shaders.builtin_functions.pack_unpack.unpacksnorm2x16_fragment = FAIL