Correct capitalisation of Xcode (#7796)

Ref: https://developer.apple.com/xcode/
diff --git a/packages/flutter_tools/lib/executable.dart b/packages/flutter_tools/lib/executable.dart
index d23b6d5..f0f4142 100644
--- a/packages/flutter_tools/lib/executable.dart
+++ b/packages/flutter_tools/lib/executable.dart
@@ -115,7 +115,7 @@
     context.putIfAbsent(ToolConfiguration, () => new ToolConfiguration());
     context.putIfAbsent(Config, () => new Config());
     context.putIfAbsent(OperatingSystemUtils, () => new OperatingSystemUtils());
-    context.putIfAbsent(XCode, () => new XCode());
+    context.putIfAbsent(Xcode, () => new Xcode());
     context.putIfAbsent(IOSSimulatorUtils, () => new IOSSimulatorUtils());
     context.putIfAbsent(SimControl, () => new SimControl());
     context.putIfAbsent(Usage, () => new Usage());
diff --git a/packages/flutter_tools/lib/src/commands/run.dart b/packages/flutter_tools/lib/src/commands/run.dart
index f0ce0c9..38385b3 100644
--- a/packages/flutter_tools/lib/src/commands/run.dart
+++ b/packages/flutter_tools/lib/src/commands/run.dart
@@ -156,7 +156,7 @@
   void printNoConnectedDevices() {
     super.printNoConnectedDevices();
     if (getCurrentHostPlatform() == HostPlatform.darwin_x64 &&
-        XCode.instance.isInstalledAndMeetsVersionCheck) {
+        Xcode.instance.isInstalledAndMeetsVersionCheck) {
       printStatus('');
       printStatus('To run on a simulator, launch it first: open -a Simulator.app');
       printStatus('');
diff --git a/packages/flutter_tools/lib/src/ios/devices.dart b/packages/flutter_tools/lib/src/ios/devices.dart
index fd7e705..f145a5a 100644
--- a/packages/flutter_tools/lib/src/ios/devices.dart
+++ b/packages/flutter_tools/lib/src/ios/devices.dart
@@ -299,7 +299,7 @@
 
     if (installationResult != 0) {
       printError('Could not install ${bundle.path} on $id.');
-      printError('Try launching XCode and selecting "Product > Run" to fix the problem:');
+      printError('Try launching Xcode and selecting "Product > Run" to fix the problem:');
       printError('  open ios/Runner.xcodeproj');
       printError('');
       return new LaunchResult.failed();
diff --git a/packages/flutter_tools/lib/src/ios/ios_workflow.dart b/packages/flutter_tools/lib/src/ios/ios_workflow.dart
index 213f505..bd55ead 100644
--- a/packages/flutter_tools/lib/src/ios/ios_workflow.dart
+++ b/packages/flutter_tools/lib/src/ios/ios_workflow.dart
@@ -13,7 +13,7 @@
 import '../doctor.dart';
 import 'mac.dart';
 
-XCode get xcode => XCode.instance;
+Xcode get xcode => Xcode.instance;
 
 class IOSWorkflow extends DoctorValidator implements Workflow {
   IOSWorkflow() : super('iOS toolchain - develop for iOS devices');
@@ -61,7 +61,7 @@
     if (xcode.isInstalled) {
       xcodeStatus = ValidationType.installed;
 
-      messages.add(new ValidationMessage('XCode at ${xcode.xcodeSelectPath}'));
+      messages.add(new ValidationMessage('Xcode at ${xcode.xcodeSelectPath}'));
 
       xcodeVersionInfo = xcode.xcodeVersionText;
       if (xcodeVersionInfo.contains(','))
@@ -71,7 +71,7 @@
       if (!xcode.isInstalledAndMeetsVersionCheck) {
         xcodeStatus = ValidationType.partial;
         messages.add(new ValidationMessage.error(
-          'Flutter requires a minimum XCode version of $kXcodeRequiredVersionMajor.$kXcodeRequiredVersionMinor.0.\n'
+          'Flutter requires a minimum Xcode version of $kXcodeRequiredVersionMajor.$kXcodeRequiredVersionMinor.0.\n'
           'Download the latest version or update via the Mac App Store.'
         ));
       }
@@ -79,13 +79,13 @@
       if (!xcode.eulaSigned) {
         xcodeStatus = ValidationType.partial;
         messages.add(new ValidationMessage.error(
-          'XCode end user license agreement not signed; open XCode or run the command \'sudo xcodebuild -license\'.'
+          'Xcode end user license agreement not signed; open Xcode or run the command \'sudo xcodebuild -license\'.'
         ));
       }
     } else {
       xcodeStatus = ValidationType.missing;
       messages.add(new ValidationMessage.error(
-        'XCode not installed; this is necessary for iOS development.\n'
+        'Xcode not installed; this is necessary for iOS development.\n'
         'Download at https://developer.apple.com/xcode/download/.'
       ));
     }
@@ -119,7 +119,7 @@
         if (result.exitCode == 0 && result.stdout.isNotEmpty && !exitsHappy(<String>['ideviceName'])) {
           brewStatus = ValidationType.partial;
           messages.add(new ValidationMessage.error(
-            'libimobiledevice is incompatible with the installed XCode version. To update, run:\n'
+            'libimobiledevice is incompatible with the installed Xcode version. To update, run:\n'
             'brew uninstall libimobiledevice\n'
             'brew install --HEAD libimobiledevice'
           ));
diff --git a/packages/flutter_tools/lib/src/ios/mac.dart b/packages/flutter_tools/lib/src/ios/mac.dart
index 13114c0..95231da 100644
--- a/packages/flutter_tools/lib/src/ios/mac.dart
+++ b/packages/flutter_tools/lib/src/ios/mac.dart
@@ -23,8 +23,8 @@
 const int kXcodeRequiredVersionMajor = 7;
 const int kXcodeRequiredVersionMinor = 0;
 
-class XCode {
-  XCode() {
+class Xcode {
+  Xcode() {
     _eulaSigned = false;
 
     try {
@@ -58,8 +58,8 @@
     }
   }
 
-  /// Returns [XCode] active in the current app context.
-  static XCode get instance => context[XCode];
+  /// Returns [Xcode] active in the current app context.
+  static Xcode get instance => context[Xcode];
 
   bool get isInstalledAndMeetsVersionCheck => isInstalled && xcodeVersionSatisfactory;
 
@@ -202,7 +202,7 @@
       printError('  ${plistFile.absolute.path}');
       printError('');
     }
-    printError("Try launching XCode and selecting 'Product > Build' to fix the problem:");
+    printError("Try launching Xcode and selecting 'Product > Build' to fix the problem:");
     printError("  open ios/Runner.xcodeproj");
     return;
   }
diff --git a/packages/flutter_tools/lib/src/ios/simulators.dart b/packages/flutter_tools/lib/src/ios/simulators.dart
index 5dffffa..4b0ec37 100644
--- a/packages/flutter_tools/lib/src/ios/simulators.dart
+++ b/packages/flutter_tools/lib/src/ios/simulators.dart
@@ -43,7 +43,7 @@
   static IOSSimulatorUtils get instance => context[IOSSimulatorUtils];
 
   List<IOSSimulator> getAttachedDevices() {
-    if (!XCode.instance.isInstalledAndMeetsVersionCheck)
+    if (!Xcode.instance.isInstalledAndMeetsVersionCheck)
       return <IOSSimulator>[];
 
     return SimControl.instance.getConnectedDevices().map((SimDevice device) {