Don't uninstall before installing in `flutter run` (#4699)

#4672

packages/flutter_tools/lib/src/commands/analyze.dart

@@ -31,8 +31,8 @@ class AnalyzeCommand extends FlutterCommand {
     argParser.addFlag('preamble', help: 'Display the number of files that will be analyzed.', defaultsTo: true);
     argParser.addFlag('congratulate', help: 'Show output even when there are no errors, warnings, hints, or lints.', defaultsTo: true);
     argParser.addFlag('watch', help: 'Run analysis continuously, watching the filesystem for changes.', negatable: false);
-    argParser.addOption('write', help: 'Also output the results to a file. This is useful with --watch if you want a file to always contain the latest results.');
-    argParser.addOption('dart-sdk', help: 'The path to the Dart SDK.', hide: true);
+    argParser.addOption('write', valueHelp: 'file', help: 'Also output the results to a file. This is useful with --watch if you want a file to always contain the latest results.');
+    argParser.addOption('dart-sdk', valueHelp: 'path-to-sdk', help: 'The path to the Dart SDK.', hide: true);
 
     // Hidden option to enable a benchmarking mode.
     argParser.addFlag('benchmark', negatable: false, hide: true);

packages/flutter_tools/lib/src/commands/install.dart

@@ -33,11 +33,11 @@ class InstallCommand extends FlutterCommand {
   }
 }
 
-bool installApp(Device device, ApplicationPackage package) {
+bool installApp(Device device, ApplicationPackage package, { bool uninstall: true }) {
   if (package == null)
     return false;
 
-  if (device.isAppInstalled(package)) {
+  if (uninstall && device.isAppInstalled(package)) {
     printStatus('Uninstalling old version...');
     if (!device.uninstallApp(package))
       printError('Warning: uninstalling old version failed');

packages/flutter_tools/lib/src/commands/run.dart

@@ -213,7 +213,7 @@ Future<int> startApp(
   if (install && device is AndroidDevice) {
     printStatus('Installing $package to $device...');
 
-    if (!(installApp(device, package)))
+    if (!(installApp(device, package, uninstall: false)))
       return 1;
   }
 

packages/flutter_tools/lib/src/run.dart

@@ -164,7 +164,7 @@ class RunAndStayResident {
     // TODO(devoncarew): This fails for ios devices - we haven't built yet.
     if (device is AndroidDevice) {
       printTrace('Running install command.');
-      if (!(installApp(device, _package)))
+      if (!(installApp(device, _package, uninstall: false)))
         return 1;
     }