Removed a text input trait that causes VoiceOver to be incorrect when tapping a text input. (flutter#17203)

Author: gaaclarke

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

@@ -7,6 +7,8 @@
 #include "flutter/shell/platform/darwin/ios/framework/Source/accessibility_bridge.h"
 #include "flutter/shell/platform/darwin/ios/framework/Source/accessibility_text_entry.h"
 
+static const UIAccessibilityTraits UIAccessibilityTraitUndocumentedEmptyLine = 0x800000000000;
+
 @implementation FlutterInactiveTextInput {
 }
 
@@ -284,8 +286,13 @@ - (UIAccessibilityTraits)accessibilityTraits {
   // Adding UIAccessibilityTraitKeyboardKey to the trait list so that iOS treats it like
   // a keyboard entry control, thus adding support for text editing features, such as
   // pinch to select text, and up/down fling to move cursor.
-  return [super accessibilityTraits] | [self textInputSurrogate].accessibilityTraits |
-         UIAccessibilityTraitKeyboardKey;
+  UIAccessibilityTraits results = [super accessibilityTraits] |
+                                  [self textInputSurrogate].accessibilityTraits |
+                                  UIAccessibilityTraitKeyboardKey;
+  // We remove an undocumented flag to get rid of a bug where single-tapping
+  // a text input field incorrectly says "empty line".
+  // See also: https://github.com/flutter/flutter/issues/52487
+  return results & (~UIAccessibilityTraitUndocumentedEmptyLine);
 }
 
 #pragma mark - UITextInput overrides