Make artifacts URLs configurable. (#13380)

Add support for configuring the base storage URL for Flutter's
artifacts. If FLUTTER_STORAGE_BASE_URL is set, use it instead of
storage.googleapis.com.

The pub server can be overridden by setting PUB_HOSTED_URL.

bin/internal/gradle_wrapper.version

-https://storage.googleapis.com/flutter_infra/gradle-wrapper/fd5c1f2c013565a3bea56ada6df9d2b8e96d56aa/gradle-wrapper.tgz
+flutter_infra/gradle-wrapper/fd5c1f2c013565a3bea56ada6df9d2b8e96d56aa/gradle-wrapper.tgz

bin/internal/material_fonts.version

-https://storage.googleapis.com/flutter_infra/flutter/fonts/13ac995daa9dda0a6ba0a45f1fccc541e616a74c/fonts.zip
+flutter_infra/flutter/fonts/13ac995daa9dda0a6ba0a45f1fccc541e616a74c/fonts.zip

bin/internal/update_dart_sdk.ps1

@@ -28,9 +28,13 @@ if ((Test-Path $dartSdkStampPath) -and ($dartSdkVersion -eq (Get-Content $dartSd
 }
 
 Write-Host "Downloading Dart SDK $dartSdkVersion..."
+$dartSdkBaseUrl = $Env:FLUTTER_STORAGE_BASE_URL
+if (-not $dartSdkBaseUrl) {
+    $dartSdkBaseUrl = "https://storage.googleapis.com"
+}
 $dartZipName = "dartsdk-windows-x64-release.zip"
 $dartChannel = if ($dartSdkVersion.Contains("-dev.")) {"dev"} else {if ($dartSdkVersion.Contains("hash/")) {"be"} else {"stable"}}
-$dartSdkUrl = "https://storage.googleapis.com/dart-archive/channels/$dartChannel/raw/$dartSdkVersion/sdk/$dartZipName"
+$dartSdkUrl = "$dartSdkBaseUrl/dart-archive/channels/$dartChannel/raw/$dartSdkVersion/sdk/$dartZipName"
 
 if (Test-Path $dartSdkPath) {
     # Move old SDK to a new location instead of deleting it in case it is still in use (e.g. by IntelliJ).

bin/internal/update_dart_sdk.sh

@@ -47,7 +47,8 @@ if [ ! -f "$DART_SDK_STAMP_PATH" ] || [ "$DART_SDK_VERSION" != `cat "$DART_SDK_S
     DART_CHANNEL="be"
   fi
 
-  DART_SDK_URL="https://storage.googleapis.com/dart-archive/channels/$DART_CHANNEL/raw/$DART_SDK_VERSION/sdk/$DART_ZIP_NAME"
+  DART_SDK_BASE_URL="${FLUTTER_STORAGE_BASE_URL:-https://storage.googleapis.com}"
+  DART_SDK_URL="$DART_SDK_BASE_URL/dart-archive/channels/$DART_CHANNEL/raw/$DART_SDK_VERSION/sdk/$DART_ZIP_NAME"
 
   # if the sdk path exists, copy it to a temporary location
   if [ -d "$DART_SDK_PATH" ]; then

dev/tools/repackage_gradle_wrapper.sh

@@ -70,7 +70,7 @@ echo "Uploading repackaged gradle wrapper..."
 echo "Content hash: $STAMP"
 gsutil.py cp -n "$WRAPPER_TEMP_DIR/gradle-wrapper.tgz" "gs://flutter_infra/gradle-wrapper/$STAMP/gradle-wrapper.tgz"
 
-echo "https://storage.googleapis.com/flutter_infra/gradle-wrapper/$STAMP/gradle-wrapper.tgz" > "$WRAPPER_VERSION_PATH"
+echo "flutter_infra/gradle-wrapper/$STAMP/gradle-wrapper.tgz" > "$WRAPPER_VERSION_PATH"
 
 rm -rf "$WRAPPER_TEMP_DIR"
 echo

packages/flutter_tools/lib/src/cache.dart

@@ -253,6 +253,28 @@ abstract class CachedArtifact {
 
   /// Template method to perform artifact update.
   Future<Null> updateInner();
+
+  String get _storageBaseUrl {
+    final String overrideUrl = platform.environment['FLUTTER_STORAGE_BASE_URL'];
+    if (overrideUrl == null)
+      return 'https://storage.googleapis.com';
+    _maybeWarnAboutStorageOverride(overrideUrl);
+    return overrideUrl;
+  }
+
+  Uri _toStorageUri(String path) => Uri.parse('$_storageBaseUrl/$path');
+}
+
+bool _hasWarnedAboutStorageOverride = false;
+
+void _maybeWarnAboutStorageOverride(String overrideUrl) {
+  if (_hasWarnedAboutStorageOverride)
+    return;
+  logger.printStatus(
+    'Flutter assets will be downloaded from $overrideUrl. Make sure you trust this source!',
+    emphasis: true,
+  );
+  _hasWarnedAboutStorageOverride = true;
 }
 
 /// A cached artifact containing fonts used for Material Design.
@@ -261,8 +283,9 @@ class MaterialFonts extends CachedArtifact {
 
   @override
   Future<Null> updateInner() {
+    final Uri archiveUri = _toStorageUri(version);
     final Status status = logger.startProgress('Downloading Material fonts...', expectSlowOperation: true);
-    return _downloadZipArchive(Uri.parse(version), location).then<Null>((_) {
+    return _downloadZipArchive(archiveUri, location).then<Null>((_) {
       status.stop();
     }).whenComplete(status.cancel);
   }
@@ -358,7 +381,7 @@ class FlutterEngine extends CachedArtifact {
 
   @override
   Future<Null> updateInner() async {
-    final String url = 'https://storage.googleapis.com/flutter_infra/flutter/$version/';
+    final String url = '$_storageBaseUrl/flutter_infra/flutter/$version/';
 
     final Directory pkgDir = cache.getCacheDir('pkg');
     for (String pkgName in _getPackageDirs()) {
@@ -410,9 +433,10 @@ class GradleWrapper extends CachedArtifact {
 
   @override
   Future<Null> updateInner() {
+    final Uri archiveUri = _toStorageUri(version);
     final Status status = logger.startProgress('Downloading Gradle Wrapper...', expectSlowOperation: true);
 
-    return _downloadZippedTarball(Uri.parse(version), location).then<Null>((_) {
+    return _downloadZippedTarball(archiveUri, location).then<Null>((_) {
       // Delete property file, allowing templates to provide it.
       fs.file(fs.path.join(location.path, 'gradle', 'wrapper', 'gradle-wrapper.properties')).deleteSync();
       // Remove NOTICE file. Should not be part of the template.

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

@@ -11,6 +11,7 @@ import 'package:meta/meta.dart';
 import '../base/file_system.dart';
 import '../base/logger.dart';
 import '../base/net.dart';
+import '../base/platform.dart';
 import '../cache.dart';
 import '../dart/pub.dart';
 import '../globals.dart';
@@ -72,7 +73,8 @@ class UpdatePackagesCommand extends FlutterCommand {
 
   Future<Null> _downloadCoverageData() async {
     final Status status = logger.startProgress('Downloading lcov data for package:flutter...', expectSlowOperation: true);
-    final List<int> data = await fetchUrl(Uri.parse('https://storage.googleapis.com/flutter_infra/flutter/coverage/lcov.info'));
+    final String urlBase = platform.environment['FLUTTER_STORAGE_BASE_URL'] ?? 'https://storage.googleapis.com';
+    final List<int> data = await fetchUrl(Uri.parse('$urlBase/flutter_infra/flutter/coverage/lcov.info'));
     final String coverageDir = fs.path.join(Cache.flutterRoot, 'packages/flutter/coverage');
     fs.file(fs.path.join(coverageDir, 'lcov.base.info'))
       ..createSync(recursive: true)