Repository: flutter
Issue: [image_picker][iOS] freeze when clicking the camera take photo button multiple times quickly
Labels: platform-ios,c: performance,p: image_picker,package,perf: speed,has reproducible steps,P2,found in release: 3.7,found in release: 3.9,team-ios,triaged-ios

Using plugin [image_picker], when presenting the camera view, clicking the take photo button multiple times quickly will lead to the application freeze at the preview page with "Retake"/"Use Photo" bottom sheet. No response when clicking the buttons on the bottom sheet.
The plugin works fine if only pressing the take photo button once.

Platform: iOS 13.3

Flutter Doctor:
```
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, v1.12.13+hotfix.5, on Mac OS X 10.14.6 18G95,
    locale en-HK)
 
[!] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
    ! Some Android licenses not accepted.  To resolve this, run: flutter doctor
      --android-licenses
[✓] Xcode - develop for iOS and macOS (Xcode 10.3)
[✓] Android Studio (version 3.4)
[✓] Connected device (1 available)
```

Logs:
```
2020-01-30 19:03:59.924768+0800 projectg_demo_ios[719:82926] [VERBOSE-2:ui_dart_state.cc(157)] Unhandled Exception: PlatformException(multiple_request, Cancelled by a second request, null)
#0      StandardMethodCodec.decodeEnvelope (package:flutter/src/services/message_codecs.dart:569:7)
#1      MethodChannel.invokeMethod (package:flutter/src/services/platform_channel.dart:321:33)
<asynchronous suspension>
#2      ImagePicker.pickImage (package:image_picker/image_picker.dart:64:40)
#3      InputBarWidgetState._openCameraBottomSheet.<anonymous closure>.<anonymous closure> (package:project_g/ui/screens/conversation/input/widget_input_bar.dart:470:51)
#4      BSCameraSelectorWidget.build.<anonymous closure> (package:project_g/ui/widgets/widget_bs_camera_selector.dart:28:15)
#5      _InkResponseState._handleTap (package:flutter/src/material/ink_well.dart:706:14)
#6      _InkResponseState.build.<anonymous closure> (package:flutter/src/material/ink_well.dart:789:36)
#7      GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:182:24)
#8      TapGestureRecognizer.handleTapUp (package:flutter/src/gestures/tap.dart:486:11)
#9      BaseTapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:264:5)
#10     BaseTapGestureRecognizer.acceptGesture (package:flutter/src/gestures/tap.dart:236:7)
#11     GestureArenaManager.sweep (package:flutter/src/gestures/arena.dart:156:27)
#12     GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:222:20)
#13     GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:198:22)
#14     GestureBinding._handlePointerEvent (package:flutter/src/gestures/binding.dart:156:7)
#15     GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:102:7)
#16     GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:86:7)
#17     _rootRunUnary (dart:async/zone.dart:1138:13)
#18     _CustomZone.runUnary (dart:async/zone.dart:1031:19)
#19     _CustomZone.runUnaryGuarded (dart:async/zone.dart:933:7)
#20     _invoke1 (dart:ui/hooks.dart:273:10)
#21     _dispatchPointerDataPacket (dart:ui/hooks.dart:182:5)
2020-01-30 19:03:59.936992+0800 projectg_demo_ios[719:82775] Warning: Attempt to present <UIImagePickerController: 0x106007000> on <FlutterViewController: 0x105882c00> whose view is not in the window hierarchy!
```

Thank you for help.