Add a new invariant declaration operator.

BUG=angle:711

Change-Id: I54a48b636a68c317b8d44ee2d578847b80095289
Reviewed-on: https://chromium-review.googlesource.com/213500
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>
diff --git a/src/compiler/translator/VersionGLSL.cpp b/src/compiler/translator/VersionGLSL.cpp
index 12dc9e0..8edbd00 100644
--- a/src/compiler/translator/VersionGLSL.cpp
+++ b/src/compiler/translator/VersionGLSL.cpp
@@ -67,6 +67,9 @@
             }
             break;
         }
+      case EOpInvariantDeclaration:
+        updateVersion(GLSL_VERSION_120);
+        break;
       case EOpParameters:
         {
             const TIntermSequence &params = *(node->getSequence());