ES31: support stencil texture via DEPTH_STENCIL_TEXTURE_MODE.

BUG=angleproject:2373

Change-Id: I5edd9db6ef6101b0ad75f71fdcdfbb1261100583
Reviewed-on: https://chromium-review.googlesource.com/936421
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libANGLE/queryutils.cpp b/src/libANGLE/queryutils.cpp
index c9d75ce..9370f4f 100644
--- a/src/libANGLE/queryutils.cpp
+++ b/src/libANGLE/queryutils.cpp
@@ -183,6 +183,10 @@
         case GL_TEXTURE_SRGB_DECODE_EXT:
             *params = CastFromGLintStateValue<ParamType>(pname, texture->getSRGBDecode());
             break;
+        case GL_DEPTH_STENCIL_TEXTURE_MODE:
+            *params =
+                CastFromGLintStateValue<ParamType>(pname, texture->getDepthStencilTextureMode());
+            break;
         default:
             UNREACHABLE();
             break;