experiment with -Wimplicit-fallthrough

net/base/gzip_header.cc

Index: net/base/gzip_header.cc
diff --git a/net/base/gzip_header.cc b/net/base/gzip_header.cc
index 88ad4d7a8408d98dbc800cfb3f153d6a0d0e7a11..d4bbf1f5a513a60c16338103a4693647bfc2e5de 100644
--- a/net/base/gzip_header.cc
+++ b/net/base/gzip_header.cc
@@ -101,7 +101,7 @@ GZipHeader::Status GZipHeader::ReadMore(const char* inbuf, int inbuf_len,
         // We intentionally fall through, because if we have a
         // zero-length FEXTRA, we want to check to notice that we're
         // done reading the FEXTRA before we exit this loop...
-
+        FALLTHROUGH_INTENDED;
       case IN_FEXTRA: {
         // Grab the rest of the bytes in the extra field, or as many
         // of them as are actually present so far.