GLES1: Shade model API

+ add sample

BUG=angleproject:2306

Change-Id: Ie0c391618ec2b771cc99b96db02b9008a86272b9
Reviewed-on: https://chromium-review.googlesource.com/1079992
Commit-Queue: Lingfeng Yang <lfy@google.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libANGLE/State.cpp b/src/libANGLE/State.cpp
index a0aacf5..a708f83 100644
--- a/src/libANGLE/State.cpp
+++ b/src/libANGLE/State.cpp
@@ -2413,6 +2413,9 @@
         case GL_MATRIX_MODE:
             *params = ToGLenum(mGLES1State.mMatrixMode);
             break;
+        case GL_SHADE_MODEL:
+            *params = ToGLenum(mGLES1State.mShadeModel);
+            break;
         default:
             UNREACHABLE();
             break;