Work more on getting things built with -Wimplicit-fallthrough.

This CL was uploaded by git cl split.

R=mkwst@chromium.org

Bug: 177475
Change-Id: I82a3074bce458d21c5a12300d54c8bf421a5b4de
Reviewed-on: https://chromium-review.googlesource.com/889948Reviewed-by: Mike West <mkwst@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532842}

third_party/WebKit/Source/core/loader/BaseFetchContext.cpp

@@ -206,6 +206,7 @@ ResourceRequestBlockedReason BaseFetchContext::CanRequestInternal(
       break;
     case Resource::kXSLStyleSheet:
       DCHECK(RuntimeEnabledFeatures::XSLTEnabled());
+      FALLTHROUGH;
     case Resource::kSVGDocument:
       if (!security_origin->CanRequest(url)) {
         PrintAccessDeniedMessage(url);

third_party/WebKit/Source/core/loader/DocumentLoader.cpp

@@ -417,7 +417,7 @@ void DocumentLoader::LoadFailed(const ResourceError& error) {
   switch (state_) {
     case kNotStarted:
       probe::frameClearedScheduledClientNavigation(frame_);
-    // Fall-through
+      FALLTHROUGH;
     case kProvisional:
       state_ = kSentDidFinishLoad;
       GetLocalFrameClient().DispatchDidFailProvisionalLoad(error,

third_party/WebKit/Source/core/loader/SubresourceFilter.cpp

@@ -102,7 +102,7 @@ void SubresourceFilter::ReportLoad(
             kOtherMessageSource, kErrorMessageLevel,
             GetErrorStringForDisallowedLoad(resource_url)));
       }
-    // fall through
+      FALLTHROUGH;
     case WebDocumentSubresourceFilter::kWouldDisallow:
       // TODO(csharrison): Consider posting a task to the main thread from
       // worker thread, or adding support for DidObserveLoadingBehavior to