ES31: Enable shader storage buffer support for OpenGL backend

BUG=angleproject:1951
TEST=angle_end2end_tests:ShaderStorageBuffer

Change-Id: I1afc3cd005ad2e595c6ce937fc53e17423f8ec8b
Reviewed-on: https://chromium-review.googlesource.com/618132
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/compiler/translator/OutputGLSLBase.cpp b/src/compiler/translator/OutputGLSLBase.cpp
index 4d3f098..4b66306 100644
--- a/src/compiler/translator/OutputGLSLBase.cpp
+++ b/src/compiler/translator/OutputGLSLBase.cpp
@@ -1237,6 +1237,12 @@
 
     out << ", ";
 
+    if (interfaceBlock->blockBinding() > 0)
+    {
+        out << "binding = " << interfaceBlock->blockBinding();
+        out << ", ";
+    }
+
     switch (interfaceBlock->matrixPacking())
     {
         case EmpUnspecified: