preprocessor: Fix lineno overflow on line continuations

BUG=chromium:774807

Change-Id: I4b3fbee31683f411810080572cfff0f8307b93bf
Reviewed-on: https://chromium-review.googlesource.com/744183
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/compiler/preprocessor/DiagnosticsBase.cpp b/src/compiler/preprocessor/DiagnosticsBase.cpp
index 1b9575b..c89bc9f 100644
--- a/src/compiler/preprocessor/DiagnosticsBase.cpp
+++ b/src/compiler/preprocessor/DiagnosticsBase.cpp
@@ -118,6 +118,8 @@
             return "extension directive must occur before any non-preprocessor tokens in ESSL3";
         case PP_UNDEFINED_SHIFT:
             return "shift exponent is negative or undefined";
+        case PP_TOKENIZER_ERROR:
+            return "internal tokenizer error";
         // Errors end.
         // Warnings begin.
         case PP_EOF_IN_DIRECTIVE: