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/preprocessor/DiagnosticsBase.h b/src/compiler/preprocessor/DiagnosticsBase.h
index a7587ed..5922d03 100644
--- a/src/compiler/preprocessor/DiagnosticsBase.h
+++ b/src/compiler/preprocessor/DiagnosticsBase.h
@@ -4,8 +4,8 @@
 // found in the LICENSE file.
 //
 
-#ifndef COMPILER_PREPROCESSOR_DIAGNOSTICS_H_
-#define COMPILER_PREPROCESSOR_DIAGNOSTICS_H_
+#ifndef COMPILER_PREPROCESSOR_DIAGNOSTICSBASE_H_
+#define COMPILER_PREPROCESSOR_DIAGNOSTICSBASE_H_
 
 #include <string>
 
@@ -84,4 +84,5 @@
 };
 
 }  // namespace pp
-#endif  // COMPILER_PREPROCESSOR_DIAGNOSTICS_H_
+
+#endif  // COMPILER_PREPROCESSOR_DIAGNOSTICSBASE_H_