Some cleanup for hot reload (#5108)

- show the next error fully after a hot reload
- hide _AssertionError in stacks
- immediately rebuild after a reassemble, so that hit tests work
- catch errors when notifying global key listeners

packages/flutter/lib/src/foundation/assertions.dart

@@ -153,6 +153,14 @@ class FlutterError extends AssertionError {
 
   static int _errorCount = 0;
 
+  /// Resets the count of errors used by [dumpErrorToConsole] to decide whether
+  /// to show a complete error message or an abbreviated one.
+  ///
+  /// After this is called, the next error message will be shown in full.
+  static void resetErrorCount() {
+    _errorCount = 0;
+  }
+
   static const int _kWrapWidth = 100;
 
   /// Prints the given exception details to the console.
@@ -163,6 +171,9 @@ class FlutterError extends AssertionError {
   /// Subsequent calls only dump the first line of the exception, unless
   /// `forceReport` is set to true (in which case it dumps the verbose message).
   ///
+  /// Call [resetErrorCount] to cause this method to go back to acting as if it
+  /// had not been called before (so the next message is verbose again).
+  ///
   /// The default behavior for the [onError] handler is to call this function.
   static void dumpErrorToConsole(FlutterErrorDetails details, { bool forceReport: false }) {
     assert(details != null);
@@ -258,17 +269,18 @@ class FlutterError extends AssertionError {
   /// format but the frame numbers will not be consecutive (frames are elided)
   /// and the final line may be prose rather than a stack frame.
   static Iterable<String> defaultStackFilter(Iterable<String> frames) {
-    final List<String> result = <String>[];
-    final List<String> filteredPackages = <String>[
+    const List<String> filteredPackages = const <String>[
       'dart:async-patch',
       'dart:async',
       'package:stack_trace',
     ];
-    final List<String> filteredClasses = <String>[
+    const List<String> filteredClasses = const <String>[
+      '_AssertionError',
       '_FakeAsync',
     ];
     final RegExp stackParser = new RegExp(r'^#[0-9]+ +([^.]+).* \(([^/]*)/[^:]+:[0-9]+(?::[0-9]+)?\)$');
     final RegExp packageParser = new RegExp(r'^([^:]+):(.+)$');
+    final List<String> result = <String>[];
     final List<String> skipped = <String>[];
     for (String line in frames) {
       Match match = stackParser.firstMatch(line);

packages/flutter/lib/src/foundation/binding.dart

@@ -119,7 +119,10 @@ abstract class BindingBase {
   /// that uses closures, so that they do not keep pointing to old
   /// code, and to flush any caches of previously computed values, in
   /// case the new code would compute them differently.
-  void reassembleApplication() { }
+  @mustCallSuper
+  void reassembleApplication() {
+    FlutterError.resetErrorCount();
+  }
 
   /// Registers a service extension method with the given name (full
   /// name "ext.flutter.name"), which takes no arguments and returns

packages/flutter/lib/src/rendering/binding.dart

@@ -165,6 +165,7 @@ abstract class RendererBinding extends BindingBase implements SchedulerBinding,
   void reassembleApplication() {
     super.reassembleApplication();
     pipelineOwner.reassemble();
+    beginFrame();
   }
 
   @override

packages/flutter/lib/src/scheduler/binding.dart

@@ -429,7 +429,7 @@ abstract class SchedulerBinding extends BindingBase {
     Duration timeStamp = _adjustForEpoch(rawTimeStamp);
     assert(() {
       if (debugPrintBeginFrameBanner)
-        print('━‬━‬━‬━‬━‬━‬━┫ Begin Frame ($timeStamp) ┣━‬━‬━‬━‬━‬━‬━');
+        print('━━━━━━━┫ Begin Frame ($timeStamp) ┣━━━━━━━');
       return true;
     });
     _lastRawTimeStamp = rawTimeStamp;

packages/flutter/lib/src/widgets/focus.dart

@@ -4,6 +4,7 @@
 
 import 'dart:async';
 
+import 'package:flutter/foundation.dart';
 import 'package:meta/meta.dart';
 
 import 'basic.dart';

packages/flutter/lib/src/widgets/framework.dart

@@ -226,6 +226,7 @@ abstract class GlobalKey<T extends State<StatefulWidget>> extends Key {
   static void unregisterRemoveListener(GlobalKey key, GlobalKeyRemoveListener listener) {
     assert(key != null);
     assert(_removeListeners.containsKey(key));
+    assert(_removeListeners[key].contains(listener));
     bool removed = _removeListeners[key].remove(listener);
     if (_removeListeners[key].isEmpty)
       _removeListeners.remove(key);
@@ -258,6 +259,8 @@ abstract class GlobalKey<T extends State<StatefulWidget>> extends Key {
             listener(key);
         }
       }
+    } catch (e, stack) {
+      _debugReportException('while notifying GlobalKey listeners', e, stack);
     } finally {
       _removedKeys.clear();
     }