[flutter_releases] Flutter stable 2.8.1 Engine Cherrypicks (#30355)

* 'Update Dart SDK to 1278bd5'

* Update cirrus secret.

* [iOS] Destroy the engine prior to application termination. (#29295)

* Update licenses hash.

* Update shell/platform/darwin/ios/framework/Source/FlutterViewControllerTest.mm

Co-authored-by: Jenn Magder <magder@google.com>

Co-authored-by: Wu Zhong <zhongwuzw@qq.com>
Co-authored-by: Jenn Magder <magder@google.com>

.cirrus.yml

@@ -1,4 +1,4 @@
-gcp_credentials: ENCRYPTED[!48cff44dd32e9cc412d4d381c7fe68d373ca04cf2639f8192d21cb1a9ab5e21129651423a1cf88f3fd7fe2125c1cabd9!]
+gcp_credentials: ENCRYPTED[!cc769765170bebc37e0556e2da5915ca64ee37f4ec8c966ec147e2f59578b476c99e457eafce4e2f8b1a4e305f7096b8!]
 
 # LINUX
 task:

DEPS

@@ -39,7 +39,7 @@ vars = {
   # Dart is: https://github.com/dart-lang/sdk/blob/main/DEPS.
   # You can use //tools/dart/create_updated_flutter_deps.py to produce
   # updated revision list of existing dependencies.
-  'dart_revision': '3d2629cd0310df74bdf260d828ed3c75f25db889',
+  'dart_revision': '1278bd5adb6a857580f137e47bc521976222f7b9',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py

ci/licenses_golden/licenses_third_party

@@ -1,4 +1,4 @@
-Signature: fbed5705076e0a8ed5942eaed257e0bc
+Signature: a92ff326020b0e5d29148bd8e830fb6c
 
 UNUSED LICENSES:
 

shell/platform/darwin/ios/framework/Source/FlutterViewController.mm

@@ -276,6 +276,11 @@ - (void)setupNotificationCenterObservers {
                  name:UIApplicationWillResignActiveNotification
                object:nil];
 
+  [center addObserver:self
+             selector:@selector(applicationWillTerminate:)
+                 name:UIApplicationWillTerminateNotification
+               object:nil];
+
   [center addObserver:self
              selector:@selector(applicationDidEnterBackground:)
                  name:UIApplicationDidEnterBackgroundNotification
@@ -790,6 +795,11 @@ - (void)applicationWillResignActive:(NSNotification*)notification {
   [self goToApplicationLifecycle:@"AppLifecycleState.inactive"];
 }
 
+- (void)applicationWillTerminate:(NSNotification*)notification {
+  [self goToApplicationLifecycle:@"AppLifecycleState.detached"];
+  [self.engine destroyContext];
+}
+
 - (void)applicationDidEnterBackground:(NSNotification*)notification {
   TRACE_EVENT0("flutter", "applicationDidEnterBackground");
   [self surfaceUpdated:NO];

shell/platform/darwin/ios/framework/Source/FlutterViewControllerTest.mm

@@ -124,6 +124,8 @@ - (void)handlePressEvent:(FlutterUIPressProxy*)press
 - (void)scrollEvent:(UIPanGestureRecognizer*)recognizer;
 - (void)updateViewportMetrics;
 - (void)onUserSettingsChanged:(NSNotification*)notification;
+- (void)applicationWillTerminate:(NSNotification*)notification;
+- (void)goToApplicationLifecycle:(nonnull NSString*)state;
 @end
 
 @interface FlutterViewControllerTest : XCTestCase
@@ -167,6 +169,20 @@ - (void)testViewDidDisappearDoesntPauseEngineWhenNotTheViewController {
   OCMReject([viewControllerMock surfaceUpdated:[OCMArg any]]);
 }
 
+- (void)testAppWillTerminateViewDidDestroyTheEngine {
+  FlutterEngine* mockEngine = OCMPartialMock([[FlutterEngine alloc] init]);
+  [mockEngine createShell:@"" libraryURI:@"" initialRoute:nil];
+  FlutterViewController* viewController = [[FlutterViewController alloc] initWithEngine:mockEngine
+                                                                                nibName:nil
+                                                                                 bundle:nil];
+  id viewControllerMock = OCMPartialMock(viewController);
+  OCMStub([viewControllerMock goToApplicationLifecycle:@"AppLifecycleState.detached"]);
+  OCMStub([mockEngine destroyContext]);
+  [viewController applicationWillTerminate:nil];
+  OCMVerify([viewControllerMock goToApplicationLifecycle:@"AppLifecycleState.detached"]);
+  OCMVerify([mockEngine destroyContext]);
+}
+
 - (void)testViewDidDisappearDoesPauseEngineWhenIsTheViewController {
   id lifecycleChannel = OCMClassMock([FlutterBasicMessageChannel class]);
   FlutterEnginePartialMock* mockEngine = [[FlutterEnginePartialMock alloc] init];