Revert "Use native async/await support in pub."

sdk/lib/_internal/pub_generated/lib/src/solver/version_solver.dart

Index: sdk/lib/_internal/pub_generated/lib/src/solver/version_solver.dart
diff --git a/sdk/lib/_internal/pub/lib/src/solver/version_solver.dart b/sdk/lib/_internal/pub_generated/lib/src/solver/version_solver.dart
similarity index 94%
copy from sdk/lib/_internal/pub/lib/src/solver/version_solver.dart
copy to sdk/lib/_internal/pub_generated/lib/src/solver/version_solver.dart
index bc2dfb12e35258c6cd3b6d5f89ea91ac543606f5..d22ace779d7fa5f61b44329bb0f273a1d9861eac 100644
--- a/sdk/lib/_internal/pub/lib/src/solver/version_solver.dart
+++ b/sdk/lib/_internal/pub_generated/lib/src/solver/version_solver.dart
@@ -36,8 +36,12 @@ Future<SolveResult> resolveVersions(SolveType type, SourceRegistry sources,
   if (useLatest == null) useLatest = [];
 
   return log.progress('Resolving dependencies', () {
-    return new BacktrackingSolver(type, sources, root, lockFile, useLatest)
-        .solve();
+    return new BacktrackingSolver(
+        type,
+        sources,
+        root,
+        lockFile,
+        useLatest).solve();
   });
 }
 
@@ -85,14 +89,15 @@ class SolveResult {
   Set<String> get changedPackages {
     if (packages == null) return null;
 
-    var changed = packages
-        .where((id) =>
-            !_sources.idsEqual(_previousLockFile.packages[id.name], id))
-        .map((id) => id.name).toSet();
+    var changed = packages.where(
+        (id) =>
+            !_sources.idsEqual(
+                _previousLockFile.packages[id.name],
+                id)).map((id) => id.name).toSet();
 
-    return changed.union(_previousLockFile.packages.keys
-        .where((package) => !availableVersions.containsKey(package))
-        .toSet());
+    return changed.union(
+        _previousLockFile.packages.keys.where(
+            (package) => !availableVersions.containsKey(package)).toSet());
   }
 
   SolveResult.success(this._sources, this._root, this._previousLockFile,
@@ -118,18 +123,21 @@ class SolveResult {
   ///
   /// [type] is the type of version resolution that was run.
   void summarizeChanges(SolveType type, {bool dryRun: false}) {
-    new SolveReport(type, _sources, _root, _previousLockFile, this)
-        .summarize(dryRun: dryRun);
+    new SolveReport(
+        type,
+        _sources,
+        _root,
+        _previousLockFile,
+        this).summarize(dryRun: dryRun);
   }
 
   String toString() {
     if (!succeeded) {
-      return 'Failed to solve after $attemptedSolutions attempts:\n'
-             '$error';
+      return 'Failed to solve after $attemptedSolutions attempts:\n' '$error';
     }
 
     return 'Took $attemptedSolutions tries to resolve to\n'
-           '- ${packages.join("\n- ")}';
+        '- ${packages.join("\n- ")}';
   }
 }
 
@@ -223,14 +231,15 @@ class PubspecCache {
     _versionCacheMisses++;
 
     var source = _sources[package.source];
-    return source.getVersions(package.name, package.description)
-        .then((versions) {
+    return source.getVersions(
+        package.name,
+        package.description).then((versions) {
       // Sort by priority so we try preferred versions first.
-      versions.sort(_type == SolveType.DOWNGRADE ? Version.antiprioritize :
-          Version.prioritize);
+      versions.sort(
+          _type == SolveType.DOWNGRADE ? Version.antiprioritize : Version.prioritize);
 
-      var ids = versions.reversed.map(
-          (version) => package.atVersion(version)).toList();
+      var ids =
+          versions.reversed.map((version) => package.atVersion(version)).toList();
       _versions[package] = ids;
       return ids;
     }).catchError((error, trace) {
@@ -463,7 +472,7 @@ class UnknownSourceException extends SolveFailure {
   String toString() {
     var dep = dependencies.single;
     return 'Package ${dep.depender} depends on ${dep.dep.name} from unknown '
-           'source "${dep.dep.source}".';
+        'source "${dep.dep.source}".';
   }
 }