Add boxing for modified variables

tests/compiler/dart2js_extra/dart2js_extra.status

Index: tests/compiler/dart2js_extra/dart2js_extra.status
diff --git a/tests/compiler/dart2js_extra/dart2js_extra.status b/tests/compiler/dart2js_extra/dart2js_extra.status
index 86b02bb8529e175efac924f6be6913decd9ae6e7..f972c89c89a30882f81e65940f564a79e5fb7032 100644
--- a/tests/compiler/dart2js_extra/dart2js_extra.status
+++ b/tests/compiler/dart2js_extra/dart2js_extra.status
@@ -182,7 +182,6 @@ regress/4562_test/01: Crash # Issue 27394
 23828_test: Crash
 assert_with_message_test: Crash
 async_stacktrace_test: Crash
-big_allocation_expression_test: Crash # 'file:*/pkg/compiler/lib/src/ssa/locals_handler.dart': Failed assertion: line 425 pos 12: '!isStoredInClosureField(local)': Local local(Maps.mapToString#first) is stored in a closure field.
 bound_closure_interceptor_methods_test: Crash
 bound_closure_interceptor_type_test: Crash
 break_test: Crash
@@ -190,11 +189,8 @@ closure3_test: Crash
 closure4_test: RuntimeError
 closure6_test: Crash
 closure7_test: Crash
-closure_capture2_test: RuntimeError
 closure_capture3_test: Crash # Assertion failure: Cannot find value Instance of 'ThisLocal' in (local(Closure.nestedClosure#)) for j:closure_call(Closure_nestedClosure_closure.call).
 closure_capture4_test: RuntimeError
-closure_capture5_test: Crash # 'file:*/pkg/compiler/lib/src/ssa/locals_handler.dart': Failed assertion: line 425 pos 12: '!isStoredInClosureField(local)': Local local(closure4#g) is stored in a closure field.
-closure_capture_test: RuntimeError
 closure_type_reflection2_test: Crash
 closure_type_reflection_test: Crash
 code_motion_exception_test: Crash
@@ -225,11 +221,9 @@ deferred_fail_and_retry_worker_test: CompileTimeError
 deferred_inheritance_test: CompileTimeError
 deferred_split_test: CompileTimeError
 dummy_compiler_test: CompileTimeError
-first_class_types_hashcode_test: Crash # 'file:*/pkg/compiler/lib/src/ssa/locals_handler.dart': Failed assertion: line 425 pos 12: '!isStoredInClosureField(local)': Local local(Maps.mapToString#first) is stored in a closure field.
 for_in_test: Crash
 hash_code_test: Crash
-if_null2_test: Crash # 'file:*/pkg/compiler/lib/src/ssa/locals_handler.dart': Failed assertion: line 425 pos 12: '!isStoredInClosureField(local)': Local local(Maps.mapToString#first) is stored in a closure field.
-if_null3_test: Crash # 'file:*/pkg/compiler/lib/src/ssa/locals_handler.dart': Failed assertion: line 425 pos 12: '!isStoredInClosureField(local)': Local local(Maps.mapToString#first) is stored in a closure field.
+closure4_test: Crash # RangeError (index): Invalid value: Only valid value is 0: 1
 if_null_test: Crash
 inference_nsm_mirrors_test: Crash
 inference_super_set_call_test: RuntimeError
@@ -322,11 +316,9 @@ closure3_test: Crash # NoSuchMethodError: Class 'KernelClosureClass' has no inst
 closure4_test: RuntimeError
 closure6_test: Crash # NoSuchMethodError: Class 'KernelClosureClass' has no instance getter 'supertype'.
 closure7_test: Crash # NoSuchMethodError: Class 'KernelClosureClass' has no instance getter 'supertype'.
-closure_capture2_test: RuntimeError
 closure_capture3_test: Crash # Assertion failure: Cannot find value local(Closure_nestedClosure_closure.call#f) in (local(Closure.nestedClosure#)) for j:closure_call(Closure_nestedClosure_closure.call).
 closure_capture4_test: RuntimeError
-closure_capture5_test: RuntimeError
-closure_capture_test: RuntimeError
+closure4_test: Crash # RangeError (index): Invalid value: Only valid value is 0: 1
 closure_type_reflection2_test: Crash # UnimplementedError: KernelClosedWorldMixin.getAppliedMixin
 closure_type_reflection_test: Crash # UnimplementedError: KernelClosedWorldMixin.getAppliedMixin
 code_motion_exception_test: Crash