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

This CL was uploaded by git cl split.

R=yosin@chromium.org

Bug: 177475
Change-Id: Ia3fdc134c6bf9a85f215156a8da48d2fcfbf4e83
Reviewed-on: https://chromium-review.googlesource.com/889962Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532303}

third_party/WebKit/Source/core/editing/state_machines/BackspaceStateMachine.cpp

@@ -193,6 +193,7 @@ TextSegmentationMachineState BackspaceStateMachine::FeedPrecedingCodeUnit(
       return MoveToNextState(BackspaceState::kOddNumberedRIS);
     case BackspaceState::kFinished:
       NOTREACHED() << "Do not call feedPrecedingCodeUnit() once it finishes.";
+      break;
     default:
       NOTREACHED() << "Unhandled state: " << state_;
   }