Implement support of unary operator "+" in translator.

BUG=angle:779
TEST=conformance/glsl/misc/struct-unary-operators.html

Change-Id: Ia827e07dcfc8ad3bbbc078e54336815be9027945
Reviewed-on: https://chromium-review.googlesource.com/222720
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Tested-by: Zhenyao Mo <zmo@chromium.org>
diff --git a/src/compiler/translator/intermOut.cpp b/src/compiler/translator/intermOut.cpp
index 56340c6..03ce5be 100644
--- a/src/compiler/translator/intermOut.cpp
+++ b/src/compiler/translator/intermOut.cpp
@@ -221,6 +221,7 @@
     switch (node->getOp())
     {
       case EOpNegative:       out << "Negate value";         break;
+      case EOpPositive:       out << "Positive sign";        break;
       case EOpVectorLogicalNot:
       case EOpLogicalNot:     out << "Negate conditional";   break;