GLES1: glMatrixMode

BUG=angleproject:2306

Change-Id: I83e15990c10d9354c2db00766ddc7b0ab960aa5c
Reviewed-on: https://chromium-review.googlesource.com/996019
Commit-Queue: Lingfeng Yang <lfy@google.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
diff --git a/src/libANGLE/State.cpp b/src/libANGLE/State.cpp
index 770aa90..914fc66 100644
--- a/src/libANGLE/State.cpp
+++ b/src/libANGLE/State.cpp
@@ -2333,6 +2333,9 @@
         case GL_CLIENT_ACTIVE_TEXTURE:
             *params = mGLES1State.mClientActiveTexture + GL_TEXTURE0;
             break;
+        case GL_MATRIX_MODE:
+            *params = ToGLenum(mGLES1State.mMatrixMode);
+            break;
         default:
             UNREACHABLE();
             break;