Issue 1:
Steps to Reproduce

Create simple Scaffold with AppBar and endDrawer. Make drawer visible. See that under transparent part of the view, in appBar, back button shows up. It might be related with #12691 issue.

Logs

Flutter Doctor

[✓] Flutter (on Linux, locale en_US.UTF-8, channel alpha)

• Flutter at /home/kamil/Flutter

• Framework revision 8f65fec (3 weeks ago), 2017-12-12 09:50:14 -0800

• Engine revision edaecdc

• Tools Dart version 1.25.0-dev.11.0

• Engine Dart version 2.0.0-edge.d8ae797298c3a6cf8dc9f4558707bd2672224d3e

[✓] Android toolchain - develop for Android devices (Android SDK 26.0.2)

• Android SDK at /home/kamil/Programs/Android/

• Android NDK at /home/kamil/Programs/Android/ndk-bundle

• Platform android-26, build-tools 26.0.2

• ANDROID_HOME = /home/kamil/Programs/Android/

• Java binary at: /home/kamil/Programs/android-studio/jre/bin/java

• Java version OpenJDK Runtime Environment (build 1.8.0_152-release-915-b01)

[✓] Android Studio (version 3.0)

• Android Studio at /home/kamil/Programs/android-studio

• Java version OpenJDK Runtime Environment (build 1.8.0_152-release-915-b01)

[✓] Connected devices

• Android SDK built for x86 • emulator-5554 • android-x86 • Android 8.0.0 (API 26) (emulator)

Issue 2:
Steps to Reproduce

Add an appBar with a title and endDrawer to a Scaffold in a LTR language (English in my case).

Observe the AppBar. No back button.

Open the endDrawer

Observe the AppBar. Back Button appears.

Not an end of the world bug by any means, but overall it looks a bit weird / causes a visual flash in the UI as the Drawer animates in smoothly and then the back button pops in all of a sudden. In addition, it can't be tapped because it's underneath the Drawer layer, so it appears to lack functional value for being there.

Might make sense to simply not show the back button in response to a Drawer being opened? Not sure what other ramifications that would have...

Thanks for your time :)

Screenshot

Flutter Doctor

[✓] Flutter (on Mac OS X 10.13.2 17C88, locale en-US, channel alpha)
• Flutter at /Users/phillywiggins/lab/flutter
• Framework revision 8f65fec5f5 (3 days ago), 2017-12-12 09:50:14 -0800
• Engine revision edaecdc8b8
• Tools Dart version 1.25.0-dev.11.0
• Engine Dart version 2.0.0-edge.d8ae797298c3a6cf8dc9f4558707bd2672224d3e

[✓] Android toolchain - develop for Android devices (Android SDK 26.0.2)
• Android SDK at /Users/phillywiggins/Library/Android/sdk
• Android NDK at /Users/phillywiggins/Library/Android/sdk/ndk-bundle
• Platform android-26, build-tools 26.0.2
• ANDROID_HOME = /Users/phillywiggins/Library/Android/sdk
• Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
• Java version OpenJDK Runtime Environment (build 1.8.0_152-release-915-b08)

[✓] iOS toolchain - develop for iOS devices (Xcode 9.2)
• Xcode at /Applications/Xcode.app/Contents/Developer
• Xcode 9.2, Build version 9C40b
• ios-deploy 1.9.2
• CocoaPods version 1.3.1

[✓] Android Studio (version 3.0)
• Android Studio at /Applications/Android Studio.app/Contents
• Java version OpenJDK Runtime Environment (build 1.8.0_152-release-915-b08)

[✓] IntelliJ IDEA Community Edition (version 2017.3.1)
• Flutter plugin version 20.0.3
• Dart plugin version 173.3942.31

[✓] Connected devices
• Android SDK built for x86 • emulator-5554 • android-x86 • Android 8.0.0 (API 26) (emulator)