Add Look Up to iOS selection controls

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

@@ -115,6 +115,9 @@ - (void)handleMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result {
     result([self clipboardHasStrings]);
   } else if ([method isEqualToString:@"LiveText.isLiveTextInputAvailable"]) {
     result(@([self isLiveTextInputAvailable]));
+  } else if ([method isEqualToString:@"LookUp.initiate"]) {
+    [self showLookUpView:args];
+    result(nil);
   } else {
     result(FlutterMethodNotImplemented);
   }
@@ -307,6 +310,13 @@ - (BOOL)isLiveTextInputAvailable {
   return [[self textField] canPerformAction:@selector(captureTextFromCamera:) withSender:nil];
 }
 
+- (void)showLookUpView:(NSString*)term {
+  UIViewController* engineViewController = [_engine.get() viewController];
+  UIReferenceLibraryViewController* refVC =
+      [[UIReferenceLibraryViewController alloc] initWithTerm:term];
+  [engineViewController presentViewController:refVC animated:YES completion:nil];
+}
+
 - (UITextField*)textField {
   if (_textField == nil) {
     _textField = [[UITextField alloc] init];

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

@@ -17,10 +17,29 @@ @interface FlutterPlatformPluginTest : XCTestCase
 
 @interface FlutterPlatformPlugin ()
 - (BOOL)isLiveTextInputAvailable;
+- (void)showLookUpView:(NSString*)term;
 @end
 
 @implementation FlutterPlatformPluginTest
 
+- (void)testLookUpCallInitiated {
+  FlutterEngine* engine = [[[FlutterEngine alloc] initWithName:@"test" project:nil] autorelease];
+  std::unique_ptr<fml::WeakPtrFactory<FlutterEngine>> _weakFactory =
+      std::make_unique<fml::WeakPtrFactory<FlutterEngine>>(engine);
+  XCTestExpectation* invokeExpectation = [self expectationWithDescription:@"isLookUpInvoked"];
+  FlutterPlatformPlugin* plugin =
+      [[[FlutterPlatformPlugin alloc] initWithEngine:_weakFactory->GetWeakPtr()] autorelease];
+  FlutterPlatformPlugin* mockPlugin = OCMPartialMock(plugin);
+  FlutterMethodCall* methodCall = [FlutterMethodCall methodCallWithMethodName:@"LookUp.initiate"
+                                                                    arguments:@"Test"];
+  FlutterResult result = ^(id result) {
+    OCMVerify([mockPlugin showLookUpView:@"Test"]);
+    [invokeExpectation fulfill];
+  };
+  [mockPlugin handleMethodCall:methodCall result:result];
+  [self waitForExpectationsWithTimeout:1 handler:nil];
+}
+
 - (void)testClipboardHasCorrectStrings {
   [UIPasteboard generalPasteboard].string = nil;
   FlutterEngine* engine = [[[FlutterEngine alloc] initWithName:@"test" project:nil] autorelease];