Fix include guards.

BUG=angle:733

Change-Id: I08b2c11c4831f1161c178c1842b10e807185aced
Reviewed-on: https://chromium-review.googlesource.com/230831
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/compiler/translator/ValidateOutputs.h b/src/compiler/translator/ValidateOutputs.h
index 0f808db..1538e0f 100644
--- a/src/compiler/translator/ValidateOutputs.h
+++ b/src/compiler/translator/ValidateOutputs.h
@@ -4,6 +4,9 @@
 // found in the LICENSE file.
 //
 
+#ifndef COMPILER_TRANSLATOR_VALIDATEOUTPUTS_H_
+#define COMPILER_TRANSLATOR_VALIDATEOUTPUTS_H_
+
 #include "compiler/translator/IntermNode.h"
 
 #include <set>
@@ -31,3 +34,5 @@
 
     void error(TSourceLoc loc, const char *reason, const char* token);
 };
+
+#endif // COMPILER_TRANSLATOR_VALIDATEOUTPUTS_H_