ES31: Add PROGRAM_SEPARABLE to ProgramParameter and GetProgram

BUG=angleproject:1939
TEST=angle_end2end_tests

Change-Id: I97ad11360f7c015947a2c0cc7d4a47f994726834
Reviewed-on: https://chromium-review.googlesource.com/454264
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
diff --git a/src/libANGLE/renderer/d3d/ProgramD3D.cpp b/src/libANGLE/renderer/d3d/ProgramD3D.cpp
index 1a28298..07db179 100644
--- a/src/libANGLE/renderer/d3d/ProgramD3D.cpp
+++ b/src/libANGLE/renderer/d3d/ProgramD3D.cpp
@@ -1128,6 +1128,10 @@
 {
 }
 
+void ProgramD3D::setSeparable(bool /* separable */)
+{
+}
+
 gl::Error ProgramD3D::getPixelExecutableForFramebuffer(const gl::Framebuffer *fbo,
                                                        ShaderExecutableD3D **outExecutable)
 {