Fix wrong state of IsolateInBackgroundNotification and IsolateInForegroundNotification.

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index 859d91381b1c290b2b14a9523656739a82bef2e7..1aad57632f4d9bc2593d6df5f08578ef8085e3f4 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -3174,12 +3174,12 @@ void Isolate::SetRAILMode(RAILMode rail_mode) {
 }
 
 void Isolate::IsolateInBackgroundNotification() {
-  is_isolate_in_background_ = false;
+  is_isolate_in_background_ = true;
   heap()->ActivateMemoryReducerIfNeeded();
 }
 
 void Isolate::IsolateInForegroundNotification() {
-  is_isolate_in_background_ = true;
+  is_isolate_in_background_ = false;
 }
 
 bool StackLimitCheck::JsHasOverflowed(uintptr_t gap) const {