Handle missing break in last switch case

pkg/compiler/lib/src/ssa/builder_kernel.dart

Index: pkg/compiler/lib/src/ssa/builder_kernel.dart
diff --git a/pkg/compiler/lib/src/ssa/builder_kernel.dart b/pkg/compiler/lib/src/ssa/builder_kernel.dart
index 75547da496dc779ee7908395b4493269eeebee09..63693bb3778341f78248442f166532f75cdd2378 100644
--- a/pkg/compiler/lib/src/ssa/builder_kernel.dart
+++ b/pkg/compiler/lib/src/ssa/builder_kernel.dart
@@ -1869,6 +1869,14 @@ class KernelSsaGraphBuilder extends ir.Visitor
       open(block);
       localsHandler = new LocalsHandler.from(savedLocals);
       buildSwitchCase(switchCase);
+      if (!isAborted() &&
+          switchCase == switchCases.last &&
+          !isDefaultCase(switchCase)) {
+        // If there is no default, we will add one later to avoid
+        // the critical edge. So we generate a break statement to make
+        // sure the last case does not fall through to the default case.
+        jumpHandler.generateBreak();
+      }
       statements.add(
           new HSubGraphBlockInformation(new SubGraph(block, lastOpenedBlock)));
     }