Fix varying interpolation parsing.

This was broken sometime in the CollectVariables refactor.

BUG=angle:803

Change-Id: Iaa09449f02290c4547f87c1560465dc8998d957c
Reviewed-on: https://chromium-review.googlesource.com/224104
Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
diff --git a/src/compiler/translator/util.cpp b/src/compiler/translator/util.cpp
index 968bbfa..8cc06a6 100644
--- a/src/compiler/translator/util.cpp
+++ b/src/compiler/translator/util.cpp
@@ -315,6 +315,8 @@
       default:
         break;
     }
+
+    variable->interpolation = GetInterpolationType(type.getQualifier());
 }
 
 template <typename VarT>