Work on getting things built with -Wimplicit-fallthrough. This CL was uploaded by git cl split.

Bug: 177475
R=msarda@chromium.org

Change-Id: Iab13eae6474e49f9890fc55f9ecf66b4ae11879d
Reviewed-on: https://chromium-review.googlesource.com/889724Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532363}

google_apis/gaia/oauth_request_signer.cc

@@ -411,7 +411,7 @@ bool OAuthRequestSigner::SignURL(
     switch (http_method) {
       case GET_METHOD:
         signed_text = request_base_url.spec() + '?';
-        // Intentionally falling through
+        FALLTHROUGH;
       case POST_METHOD:
         signed_text += BuildBaseStringParameters(parameters);
         break;