Spelling (#15229)

* spelling: accommodate

* spelling: allotted

* spelling: anonymous

* spelling: artificial

* spelling: associated

* spelling: asset

* spelling: button

* spelling: canvas

* spelling: compatibility

* spelling: coverage

* spelling: condition

* spelling: decoration

* spelling: deferring

* spelling: diameter

* spelling: direction

* spelling: displacement

* spelling: dropdown

* spelling: needing

* spelling: environment

* spelling: exited

* spelling: expansion

* spelling: explore

* spelling: families

* spelling: horizontal

* spelling: increment

* spelling: indices

* spelling: internationalization

* spelling: labrador

* spelling: localizations

* spelling: midflight

* spelling: milliseconds

* spelling: minimum

* spelling: multiple

* spelling: multiplication

* spelling: navigator

* spelling: overridden

* spelling: package

* spelling: performance

* spelling: platform

* spelling: porsche

* spelling: position

* spelling: preceded

* spelling: precede

* spelling: precedence

* spelling: print

* spelling: property

* spelling: readily

* spelling: reproducibility

* spelling: rounded

* spelling: scroll

* spelling: separate

* spelling: separator

* spelling: services

* spelling: specific

* spelling: specify

* spelling: synchronously

* spelling: through

* spelling: timeout

* spelling: triangle

* spelling: trivial

* spelling: unusual

* spelling: then

* spelling: vertically

* spelling: visible

* spelling: visited

* spelling: voice
diff --git a/packages/flutter_tools/test/dart/pub_get_test.dart b/packages/flutter_tools/test/dart/pub_get_test.dart
index 0e6b90a..2dcbe6d 100644
--- a/packages/flutter_tools/test/dart/pub_get_test.dart
+++ b/packages/flutter_tools/test/dart/pub_get_test.dart
@@ -31,7 +31,7 @@
     final MockProcessManager processMock = context.getVariable(ProcessManager);
 
     new FakeAsync().run((FakeAsync time) {
-      expect(processMock.lastPubEnvironmment, isNull);
+      expect(processMock.lastPubEnvironment, isNull);
       expect(testLogger.statusText, '');
       pubGet(context: PubContext.flutterTests, checkLastModified: false).then((Null value) {
         error = 'test completed unexpectedly';
@@ -43,7 +43,7 @@
         'Running "flutter packages get" in /...\n'
         'pub get failed (69) -- attempting retry 1 in 1 second...\n'
       );
-      expect(processMock.lastPubEnvironmment, contains('flutter_cli:flutter_tests'));
+      expect(processMock.lastPubEnvironment, contains('flutter_cli:flutter_tests'));
       expect(processMock.lastPubCache, isNull);
       time.elapse(const Duration(milliseconds: 500));
       expect(testLogger.statusText,
@@ -101,7 +101,7 @@
 
     new FakeAsync().run((FakeAsync time) {
       MockDirectory.findCache = true;
-      expect(processMock.lastPubEnvironmment, isNull);
+      expect(processMock.lastPubEnvironment, isNull);
       expect(processMock.lastPubCache, isNull);
       pubGet(context: PubContext.flutterTests, checkLastModified: false).then((Null value) {
         error = 'test completed unexpectedly';
@@ -127,7 +127,7 @@
 
     new FakeAsync().run((FakeAsync time) {
       MockDirectory.findCache = true;
-      expect(processMock.lastPubEnvironmment, isNull);
+      expect(processMock.lastPubEnvironment, isNull);
       expect(processMock.lastPubCache, isNull);
       pubGet(context: PubContext.flutterTests, checkLastModified: false).then((Null value) {
         error = 'test completed unexpectedly';
@@ -154,7 +154,7 @@
 
   final int fakeExitCode;
 
-  String lastPubEnvironmment;
+  String lastPubEnvironment;
   String lastPubCache;
 
   @override
@@ -166,7 +166,7 @@
     bool runInShell: false,
     ProcessStartMode mode: ProcessStartMode.NORMAL,
   }) {
-    lastPubEnvironmment = environment['PUB_ENVIRONMENT'];
+    lastPubEnvironment = environment['PUB_ENVIRONMENT'];
     lastPubCache = environment['PUB_CACHE'];
     return new Future<Process>.value(new MockProcess(fakeExitCode));
   }
diff --git a/packages/flutter_tools/test/devfs_test.dart b/packages/flutter_tools/test/devfs_test.dart
index a4b413e..6252f45 100644
--- a/packages/flutter_tools/test/devfs_test.dart
+++ b/packages/flutter_tools/test/devfs_test.dart
@@ -123,9 +123,9 @@
       FileSystem: () => fs,
     });
 
-    testUsingContext('add new file to local file system and preserve unusal file name casing', () async {
-      final String filePathWithUnusalCasing = fs.path.join('FooBar', 'TEST.txt');
-      final File file = fs.file(fs.path.join(basePath, filePathWithUnusalCasing));
+    testUsingContext('add new file to local file system and preserve unusual file name casing', () async {
+      final String filePathWithUnusualCasing = fs.path.join('FooBar', 'TEST.txt');
+      final File file = fs.file(fs.path.join(basePath, filePathWithUnusualCasing));
       await file.parent.create(recursive: true);
       file.writeAsBytesSync(<int>[1, 2, 3, 4, 5, 6, 7]);
       final int bytes = await devFS.update();
diff --git a/packages/flutter_tools/test/flutter_manifest_test.dart b/packages/flutter_tools/test/flutter_manifest_test.dart
index 56e7a99..af988e3 100644
--- a/packages/flutter_tools/test/flutter_manifest_test.dart
+++ b/packages/flutter_tools/test/flutter_manifest_test.dart
@@ -240,7 +240,7 @@
       expect(barFontAsset1.style, 'italic');
     });
 
-    testUsingContext('has only one of two font familes when one declaration is missing the "family" option', () async {
+    testUsingContext('has only one of two font families when one declaration is missing the "family" option', () async {
       const String manifest = '''
 name: test
 dependencies:
@@ -285,7 +285,7 @@
       expect(fooFontAsset1.style, 'italic');
     });
 
-    testUsingContext('has only one of two font familes when one declaration is missing the "fonts" option', () async {
+    testUsingContext('has only one of two font families when one declaration is missing the "fonts" option', () async {
       const String manifest = '''
 name: test
 dependencies: