Implement fall-through errors.

test/kernel/regression/switch_execution_case_t02.dart.txt

+library;
+import self as self;
+import "dart:core" as core;
+
+static method test(dynamic value) → dynamic {
+  dynamic result;
+  #L1:
+  switch(value) {
+    #L2:
+    case 1:
+      {
+        result = 1;
+        break #L1;
+      }
+    #L3:
+    case 2:
+      {
+        result = 2;
+        throw core::_fallThroughError();
+      }
+    #L4:
+    case 3:
+      {
+        result = 3;
+        throw core::_fallThroughError();
+      }
+    #L5:
+    default:
+      {
+        result = 4;
+        throw core::_fallThroughError();
+      }
+  }
+  return result;
+}
+static method testEmptyCases(dynamic value) → dynamic {
+  dynamic result;
+  #L6:
+  switch(value) {
+    #L7:
+    case 1:
+    case 2:
+      {
+        result = 1;
+        throw core::_fallThroughError();
+      }
+    #L8:
+    case 3:
+    case 4:
+      {
+        result = 2;
+        break #L6;
+      }
+    #L9:
+    case 5:
+    case 6:
+    default:
+      throw core::_fallThroughError();
+  }
+  return result;
+}
+static method main() → dynamic {}