dart2dart: Test cases for better code coverage in dart_tree rewritings.

sdk/lib/_internal/compiler/implementation/dart_backend/dart_tree.dart

Index: sdk/lib/_internal/compiler/implementation/dart_backend/dart_tree.dart
diff --git a/sdk/lib/_internal/compiler/implementation/dart_backend/dart_tree.dart b/sdk/lib/_internal/compiler/implementation/dart_backend/dart_tree.dart
index 51eec0e2ff3289d46f28b249c1c3c78bfe15efd8..5f00ae34f4c14f1debd39ee0803772d59e65bbaa 100644
--- a/sdk/lib/_internal/compiler/implementation/dart_backend/dart_tree.dart
+++ b/sdk/lib/_internal/compiler/implementation/dart_backend/dart_tree.dart
@@ -1402,7 +1402,7 @@ class LogicalRewriter extends Visitor<Statement, Expression> {
           putInBooleanContext(node.elseExpression));
     }
     // x ? false : y ==> !x && y  (if y is known to be a boolean)
-    if (isBooleanValued(node.elseExpression) && isTrue(node.thenExpression)) {
+    if (isBooleanValued(node.elseExpression) && isFalse(node.thenExpression)) {
       return new LogicalOperator.and(
           makeCondition(node.condition, false, liftNots: false),
           putInBooleanContext(node.elseExpression));