[vm] Allow for long jumps during reusable handle scopes.

Such long jumps may occur due to Out Of Memory exceptions.

TEST=run test harness with low heap limit
Change-Id: Ifc8d062d4325ea3cdb4ea1f1ad1877f2dc83229e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/213534
Reviewed-by: Siva Annamalai <[email protected]>
Commit-Queue: Ryan Macnak <[email protected]>

Author: rmacnak-google

runtime/vm/longjump.cc

@@ -36,13 +36,6 @@ void LongJumpScope::Jump(int value) {
   Thread* thread = Thread::Current();
   DEBUG_ASSERT(thread->TopErrorHandlerIsSetJump());
 
-#if defined(DEBUG)
-#define CHECK_REUSABLE_HANDLE(name)                                            \
-  ASSERT(!thread->reusable_##name##_handle_scope_active());
-  REUSABLE_HANDLE_LIST(CHECK_REUSABLE_HANDLE)
-#undef CHECK_REUSABLE_HANDLE
-#endif  // defined(DEBUG)
-
   // Destruct all the active StackResource objects.
   StackResource::UnwindAbove(thread, top_);
   longjmp(environment_, value);

runtime/vm/reusable_handles.h

@@ -32,16 +32,13 @@ namespace dart {
 
 #if defined(DEBUG)
 #define REUSABLE_SCOPE(name)                                                   \
-  class Reusable##name##HandleScope : public ValueObject {                     \
+  class Reusable##name##HandleScope : public StackResource {                   \
    public:                                                                     \
-    explicit Reusable##name##HandleScope(Thread* thread) : thread_(thread) {   \
+    explicit Reusable##name##HandleScope(Thread* thread = Thread::Current())   \
+        : StackResource(thread), thread_(thread) {                             \
       ASSERT(!thread->reusable_##name##_handle_scope_active());                \
       thread->set_reusable_##name##_handle_scope_active(true);                 \
     }                                                                          \
-    Reusable##name##HandleScope() : thread_(Thread::Current()) {               \
-      ASSERT(!thread_->reusable_##name##_handle_scope_active());               \
-      thread_->set_reusable_##name##_handle_scope_active(true);                \
-    }                                                                          \
     ~Reusable##name##HandleScope() {                                           \
       ASSERT(thread_->reusable_##name##_handle_scope_active());                \
       thread_->set_reusable_##name##_handle_scope_active(false);               \
@@ -60,10 +57,8 @@ namespace dart {
 #define REUSABLE_SCOPE(name)                                                   \
   class Reusable##name##HandleScope : public ValueObject {                     \
    public:                                                                     \
-    explicit Reusable##name##HandleScope(Thread* thread)                       \
+    explicit Reusable##name##HandleScope(Thread* thread = Thread::Current())   \
         : handle_(thread->name##_handle_) {}                                   \
-    Reusable##name##HandleScope()                                              \
-        : handle_(Thread::Current()->name##_handle_) {}                        \
     ~Reusable##name##HandleScope() { handle_->ptr_ = name::null(); }           \
     name& Handle() const {                                                     \
       ASSERT(handle_ != NULL);                                                 \