Remove the assembleFlx accessor and FLX asset path overrides (#4671)

This is now obsolete
diff --git a/packages/flutter_tools/lib/flutter_tools.dart b/packages/flutter_tools/lib/flutter_tools.dart
deleted file mode 100644
index e37cd6d..0000000
--- a/packages/flutter_tools/lib/flutter_tools.dart
+++ /dev/null
@@ -1,28 +0,0 @@
-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-import 'dart:async';
-import 'dart:io';
-
-import 'src/flx.dart' as flx;
-
-/// Assembles a Flutter .flx file from a pre-existing manifest descriptor and a
-/// pre-compiled snapshot.
-Future<int> assembleFlx({
-  Map<String, dynamic> manifestDescriptor: const <String, dynamic>{},
-  File snapshotFile: null,
-  String assetBasePath: flx.defaultAssetBasePath,
-  Map<String, String> assetPathOverrides: const <String, String>{},
-  String outputPath: flx.defaultFlxOutputPath,
-  String privateKeyPath: flx.defaultPrivateKeyPath
-}) async {
-  return flx.assemble(
-    manifestDescriptor: manifestDescriptor,
-    snapshotFile: snapshotFile,
-    assetBasePath: assetBasePath,
-    assetPathOverrides: assetPathOverrides,
-    outputPath: outputPath,
-    privateKeyPath: privateKeyPath
-  );
-}
diff --git a/packages/flutter_tools/lib/src/flx.dart b/packages/flutter_tools/lib/src/flx.dart
index 8c8e7a5..de03875 100644
--- a/packages/flutter_tools/lib/src/flx.dart
+++ b/packages/flutter_tools/lib/src/flx.dart
@@ -127,8 +127,7 @@
 Map<_Asset, List<_Asset>> _parseAssets(
   PackageMap packageMap,
   Map<String, dynamic> manifestDescriptor,
-  String assetBase,
-  Map<String, String> assetPathOverrides, {
+  String assetBase, {
   List<String> excludeDirs: const <String>[]
 }) {
   Map<_Asset, List<_Asset>> result = <_Asset, List<_Asset>>{};
@@ -141,7 +140,7 @@
 
   if (manifestDescriptor.containsKey('assets')) {
     for (String asset in manifestDescriptor['assets']) {
-      _Asset baseAsset = _resolveAsset(packageMap, assetBase, assetPathOverrides, asset);
+      _Asset baseAsset = _resolveAsset(packageMap, assetBase, asset);
 
       if (!baseAsset.assetFileExists) {
         printError('Error: unable to locate asset entry in flutter.yaml: "$asset".');
@@ -187,7 +186,7 @@
         String asset = font['asset'];
         if (asset == null) continue;
 
-        _Asset baseAsset = _resolveAsset(packageMap, assetBase, assetPathOverrides, asset);
+        _Asset baseAsset = _resolveAsset(packageMap, assetBase, asset);
         if (!baseAsset.assetFileExists) {
           printError('Error: unable to locate asset entry in flutter.yaml: "$asset".');
           return null;
@@ -204,18 +203,8 @@
 _Asset _resolveAsset(
   PackageMap packageMap,
   String assetBase,
-  Map<String, String> assetPathOverrides,
   String asset
 ) {
-  String overridePath = assetPathOverrides[asset];
-  if (overridePath != null) {
-    return new _Asset(
-      base: path.dirname(overridePath),
-      source: path.basename(overridePath),
-      relativePath: asset
-    );
-  }
-
   if (asset.startsWith('packages/') && !FileSystemEntity.isFileSync(path.join(assetBase, asset))) {
     // Convert packages/flutter_gallery_assets/clouds-0.png to clouds-0.png.
     String packageKey = asset.substring(9);
@@ -387,7 +376,6 @@
   Map<String, dynamic> manifestDescriptor: const <String, dynamic>{},
   File snapshotFile,
   String assetBasePath: defaultAssetBasePath,
-  Map<String, String> assetPathOverrides: const <String, String>{},
   String outputPath: defaultFlxOutputPath,
   String privateKeyPath: defaultPrivateKeyPath,
   String workingDirPath: defaultWorkingDirPath,
@@ -399,7 +387,6 @@
     new PackageMap(path.join(assetBasePath, '.packages')),
     manifestDescriptor,
     assetBasePath,
-    assetPathOverrides,
     excludeDirs: <String>[workingDirPath, path.join(assetBasePath, 'build')]
   );