Implement GL_EXT_debug_marker in D3D9/D3D11 renderers

BUG=angleproject:1043

Change-Id: I7f3bfb35050662520b901828d0478719fa8d11b3
Reviewed-on: https://chromium-review.googlesource.com/274054
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Austin Kinross <aukinros@microsoft.com>
diff --git a/src/libANGLE/renderer/gl/RendererGL.cpp b/src/libANGLE/renderer/gl/RendererGL.cpp
index 7acb492..9459422 100644
--- a/src/libANGLE/renderer/gl/RendererGL.cpp
+++ b/src/libANGLE/renderer/gl/RendererGL.cpp
@@ -230,6 +230,21 @@
     return new TransformFeedbackGL();
 }
 
+void RendererGL::insertEventMarker(GLsizei, const char *)
+{
+    UNREACHABLE();
+}
+
+void RendererGL::pushGroupMarker(GLsizei, const char *)
+{
+    UNREACHABLE();
+}
+
+void RendererGL::popGroupMarker()
+{
+    UNREACHABLE();
+}
+
 void RendererGL::notifyDeviceLost()
 {
     UNIMPLEMENTED();