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

This CL was uploaded by git cl split.

R=raymes@chromium.org

Bug: 177475
Change-Id: I8f6b7f32865c6a8c5f4db94bbd5c0a61296f7876
Reviewed-on: https://chromium-review.googlesource.com/889947Reviewed-by: Raymes Khoury <raymes@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532929}

content/renderer/pepper/content_renderer_pepper_host_factory.cc

@@ -197,10 +197,12 @@ ContentRendererPepperHostFactory::CreateResourceHost(
       if (CanUseMediaStreamAPI(host_, instance))
         return std::make_unique<PepperVideoDestinationHost>(host_, instance,
                                                             resource);
+      return nullptr;
     case PpapiHostMsg_VideoSource_Create::ID:
       if (CanUseMediaStreamAPI(host_, instance))
         return std::make_unique<PepperVideoSourceHost>(host_, instance,
                                                        resource);
+      return nullptr;
 #endif  // BUILDFLAG(ENABLE_WEBRTC)
   }