Fix and enable warning C4244 (Conversion from 'type1' to 'type2', possible loss of data)

Change-Id: Id0e06d7d6600344d858f00dabc219d79289bbc82
Reviewed-on: https://chromium-review.googlesource.com/265020
Tested-by: Minmin Gong <mgong@microsoft.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
diff --git a/src/compiler/preprocessor/Tokenizer.l b/src/compiler/preprocessor/Tokenizer.l
index 89cb5c8..bfc503e 100644
--- a/src/compiler/preprocessor/Tokenizer.l
+++ b/src/compiler/preprocessor/Tokenizer.l
@@ -31,6 +31,8 @@
 #if defined(__GNUC__)
 // Triggered by the auto-generated yy_fatal_error function.
 #pragma GCC diagnostic ignored "-Wmissing-noreturn"
+#elif defined(_MSC_VER)
+#pragma warning(disable: 4244)
 #endif
 
 typedef std::string YYSTYPE;