Issue 1:
Steps to Reproduce

...

...

...

Logs

Launching lib\main.dart on Lenovo K50a40 in debug mode...

Compiler message:
file:///C:/flutter/packages/flutter/lib/src/material/text_field.dart:104:10: Error: Duplicated parameter name 'controller'.
this.controller,
^^^^^^^^^^
file:///C:/flutter/packages/flutter/lib/src/material/text_field.dart:102:41: Context: Other parameter named 'controller'.
const TextField(TextEditingController controller, {
^^^^^^^^^^
file:///C:/flutter/packages/flutter/lib/src/material/search.dart:433:27: Error: Too few positional arguments: 1 required, 0 given.
title: TextField(
^
file:///C:/flutter/packages/flutter/lib/src/material/text_field.dart:102:9: Context: Found this candidate, but the arguments don't match.
const TextField(TextEditingController controller, {
^
file:///C:/flutter/packages/flutter/lib/src/material/text_form_field.dart:123:23: Error: Too few positional arguments: 1 required, 0 given.
return TextField(
^
file:///C:/flutter/packages/flutter/lib/src/material/text_field.dart:102:9: Context: Found this candidate, but the arguments don't match.
const TextField(TextEditingController controller, {
^
Compiler failed on D:\bbb\lib\main.dart
Gradle task assembleDebug failed with exit code 1
Exited (sigterm)

Issue 2:
I was evaluating using Flutter with the Flutter Gallery for look / feel before using it when I found this bug.

Flutter crashes in the 'Studies' > 'Contact Profile' section after rapidly scrolling up / down and repeatedly selecting an app bar option from the menu in the upper right-hand corner.

The stack trace from the flutter command line app is as follows:

I/flutter (31551): ══╡ EXCEPTION CAUGHT BY FOUNDATION LIBRARY ╞════════════════════════════════════════════════════════
I/flutter (31551): The following NoSuchMethodError was thrown while dispatching notifications for ValueNotifier<bool>:
I/flutter (31551): The method 'stop' was called on null.
I/flutter (31551): Receiver: null
I/flutter (31551): Tried calling: stop(canceled: true)
I/flutter (31551):
I/flutter (31551): When the exception was thrown, this was the stack:
I/flutter (31551): #0 Object.noSuchMethod (dart:core/runtime/libobject_patch.dart:46:5)
I/flutter (31551): #1 AnimationController.stop (package:flutter/src/animation/animation_controller.dart:499:13)
I/flutter (31551): #2 RenderSliverFloatingPersistentHeader.maybeStopSnapAnimation (package:flutter/src/rendering/sliver_persistent_header.dart:457:18)
I/flutter (31551): #3 _FloatingAppBarState._isScrollingListener (package:flutter/src/material/app_bar.dart:548:15)
I/flutter (31551): #4 ChangeNotifier.notifyListeners (package:flutter/src/foundation/change_notifier.dart:161:21)
I/flutter (31551): #5 ValueNotifier.value= (package:flutter/src/foundation/change_notifier.dart:217:5)
I/flutter (31551): #6 ScrollPosition.beginActivity (package:flutter/src/widgets/scroll_position.dart:583:25)
I/flutter (31551): #7 ScrollPositionWithSingleContext.beginActivity (package:flutter/src/widgets/scroll_position_with_single_context.dart:122:11)
I/flutter (31551): #8 ScrollPositionWithSingleContext.drag (package:flutter/src/widgets/scroll_position_with_single_context.dart:250:5)
I/flutter (31551): #9 ScrollableState._handleDragStart (package:flutter/src/widgets/scrollable.dart:443:22)
I/flutter (31551): #10 DragGestureRecognizer.acceptGesture.<anonymous closure> (package:flutter/src/gestures/monodrag.dart:169:47)
I/flutter (31551): #11 GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:102:24)
I/flutter (31551): #12 DragGestureRecognizer.acceptGesture (package:flutter/src/gestures/monodrag.dart:169:9)
I/flutter (31551): #13 GestureArenaManager._resolveByDefault (package:flutter/src/gestures/arena.dart:250:25)
I/flutter (31551): #14 GestureArenaManager._tryToResolveArena.<anonymous closure> (package:flutter/src/gestures/arena.dart:231:31)
I/flutter (31551): (elided 2 frames from package dart:async)
I/flutter (31551):
I/flutter (31551): The ValueNotifier<bool> sending notification was:
I/flutter (31551): ValueNotifier<bool>#152a4(true)
I/flutter (31551): ════════════════════════════════════════════════════════════════════════════════════════════════════
I/flutter (31551): Another exception was thrown: AnimationController.dispose() called more than once.
I/flutter (31551): Another exception was thrown: A RenderViewport expected a child of type RenderSliver but received a child of type RenderErrorBox.
I/flutter (31551): Another exception was thrown: A RenderViewport expected a child of type RenderSliver but received a child of type RenderErrorBox.
I/flutter (31551): Another exception was thrown: A RenderViewport expected a child of type RenderSliver but received a child of type RenderErrorBox.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3497 pos 14: 'owner._debugCurrentBuildTarget == this': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 4681 pos 12: 'renderObject.child == child': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 4681 pos 12: 'renderObject.child == child': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 4062 pos 14: '() {
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 2240 pos 16: '!_dirtyElements[index]._active || _dirtyElements[index]._debugIsInScope(context)': is not true.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3681 pos 12: 'child == _child': is not true.
I/flutter (31551): Another exception was thrown: Duplicate GlobalKey detected in widget tree.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3681 pos 12: 'child == _child': is not true.
I/flutter (31551): Another exception was thrown: Duplicate GlobalKey detected in widget tree.
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3681 pos 12: 'child == _child': is not true.
I/flutter (31551): Another exception was thrown: Duplicate GlobalKey detected in widget tree.
I/FlutterActivityDelegate(31551): onResume setting current activity to this
I/OpenGLRenderer(31551): Initialized EGL, version 1.4
D/OpenGLRenderer(31551): Swap behavior 1
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3681 pos 12: 'child == _child': is not true.
I/flutter (31551): Another exception was thrown: Duplicate GlobalKey detected in widget tree.
I/FlutterActivityDelegate(31551): onResume setting current activity to this
I/FlutterActivityDelegate(31551): onResume setting current activity to this
I/OpenGLRenderer(31551): Initialized EGL, version 1.4
D/OpenGLRenderer(31551): Swap behavior 1
I/flutter (31551): Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3681 pos 12: 'child == _child': is not true.
I/flutter (31551): Another exception was thrown: Duplicate GlobalKey detected in widget tree.

Is this an issue that's only possible due to the nature of the example changing the app bar behavior? This bug can also be found in the version of the example found in the Google Play store (I found it first there, then installed via github to produce a stack trace). Bug was found on version 0.4.2 on a Nexus 6P.