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/Intermediate.cpp b/src/compiler/translator/Intermediate.cpp
index ef4f833..e558683 100644
--- a/src/compiler/translator/Intermediate.cpp
+++ b/src/compiler/translator/Intermediate.cpp
@@ -198,6 +198,7 @@
       case EOpPostDecrement:
       case EOpPreDecrement:
       case EOpNegative:
+      case EOpPositive:
         if (child->getType().getBasicType() == EbtStruct ||
             child->getType().isArray())
         {