Plumb --extra-front-end-options in flutter build bundle (#17404)

packages/flutter_tools/gradle/flutter.gradle

@@ -458,6 +458,9 @@ abstract class BaseFlutterTask extends DefaultTask {
             if (trackWidgetCreation) {
                 args "--track-widget-creation"
             }
+            if (extraFrontEndOptions != null) {
+                args "--extra-front-end-options", "${extraFrontEndOptions}"
+            }
             if (buildMode != "debug") {
                 args "--precompiled"
             } else {

packages/flutter_tools/lib/src/bundle.dart

@@ -41,6 +41,7 @@ Future<void> build({
   bool precompiledSnapshot: false,
   bool reportLicensedPackages: false,
   bool trackWidgetCreation: false,
+  List<String> extraFrontEndOptions: const <String>[],
   List<String> fileSystemRoots,
   String fileSystemScheme,
 }) async {
@@ -70,6 +71,8 @@ Future<void> build({
 
   DevFSContent kernelContent;
   if (!precompiledSnapshot && previewDart2) {
+    if ((extraFrontEndOptions != null) && extraFrontEndOptions.isNotEmpty)
+      printTrace('Extra front-end options: $extraFrontEndOptions');
     ensureDirectoryExists(applicationKernelFilePath);
     final CompilerOutput compilerOutput = await kernelCompiler.compile(
       sdkRoot: artifacts.getArtifactPath(Artifact.flutterPatchedSdkPath),
@@ -78,6 +81,7 @@ Future<void> build({
       outputFilePath: applicationKernelFilePath,
       depFilePath: depfilePath,
       trackWidgetCreation: trackWidgetCreation,
+      extraFrontEndOptions: extraFrontEndOptions,
       fileSystemRoots: fileSystemRoots,
       fileSystemScheme: fileSystemScheme,
       packagesPath: packagesPath,

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

@@ -6,6 +6,7 @@ import 'dart:async';
 
 import '../build_info.dart';
 import '../bundle.dart';
+import '../runner/flutter_command.dart' show FlutterOptions;
 import 'build.dart';
 
 class BuildBundleCommand extends BuildSubCommand {
@@ -30,6 +31,10 @@ class BuildBundleCommand extends BuildSubCommand {
         hide: !verboseHelp,
         help: 'Track widget creation locations. Requires Dart 2.0 functionality.',
       )
+      ..addMultiOption(FlutterOptions.kExtraFrontEndOptions,
+        splitCommas: true,
+        hide: true,
+      )
       ..addOption('asset-dir', defaultsTo: getAssetBuildDirectory())
       ..addFlag('report-licensed-packages',
         help: 'Whether to report the names of all the packages that are included '
@@ -76,6 +81,7 @@ class BuildBundleCommand extends BuildSubCommand {
       precompiledSnapshot: argResults['precompiled'],
       reportLicensedPackages: argResults['report-licensed-packages'],
       trackWidgetCreation: argResults['track-widget-creation'],
+      extraFrontEndOptions: argResults[FlutterOptions.kExtraFrontEndOptions],
       fileSystemScheme: argResults['filesystem-scheme'],
       fileSystemRoots: argResults['filesystem-root'],
     );