Revert "Add support for parsing ESSL3 invariant qualifiers"

Build breaks in GPU FYI bots.

BUG=angleproject:987

This reverts commit 4008879357159c7850cf105f2ae842bc68dd3c18.

Change-Id: Ia88ad302c403c65516c050eb7741316b5097bcfb
Reviewed-on: https://chromium-review.googlesource.com/269847
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>
diff --git a/src/compiler/translator/ShaderVars.cpp b/src/compiler/translator/ShaderVars.cpp
index 207ae22..590655f 100644
--- a/src/compiler/translator/ShaderVars.cpp
+++ b/src/compiler/translator/ShaderVars.cpp
@@ -303,11 +303,11 @@
             isInvariant == other.isInvariant);
 }
 
-bool Varying::isSameVaryingAtLinkTime(const Varying &other, int shaderVersion) const
+bool Varying::isSameVaryingAtLinkTime(const Varying &other) const
 {
     return (ShaderVariable::isSameVariableAtLinkTime(other, false) &&
             interpolation == other.interpolation &&
-            (shaderVersion >= 300 || isInvariant == other.isInvariant));
+            isInvariant == other.isInvariant);
 }
 
 InterfaceBlock::InterfaceBlock()