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

Bug: 177475
R=pfeldman@chromium.org

Change-Id: I8f9cf8c5f1c07eec6c9571b1c1e25d39b7e0f93a
Reviewed-on: https://chromium-review.googlesource.com/889843Reviewed-by: Pavel Feldman <pfeldman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532112}

third_party/WebKit/Source/platform/DateComponents.cpp

@@ -687,7 +687,7 @@ String DateComponents::ToStringForTime(SecondFormat format) const {
   switch (effective_format) {
     default:
       NOTREACHED();
-    // Fallback to None.
+      FALLTHROUGH;
     case kNone:
       return String::Format("%02d:%02d", hour_, minute_);
     case kSecond: