Make pub's binstubs resilient to changes in snapshot format.

sdk/lib/_internal/pub_generated/lib/src/entrypoint.dart

Index: sdk/lib/_internal/pub_generated/lib/src/entrypoint.dart
diff --git a/sdk/lib/_internal/pub_generated/lib/src/entrypoint.dart b/sdk/lib/_internal/pub_generated/lib/src/entrypoint.dart
index ee16741b513fcba1edeb188f443270d51a07b9f7..a6b8f890889fef7fb1cf3d9e347b76ebf27426f1 100644
--- a/sdk/lib/_internal/pub_generated/lib/src/entrypoint.dart
+++ b/sdk/lib/_internal/pub_generated/lib/src/entrypoint.dart
@@ -50,6 +50,12 @@ class Entrypoint {
   /// the installed packages.
   final bool _packageSymlinks;
 
+  /// Whether this entrypoint is in-memory and doesn't correspond to a user's
+  /// package directory on disk (for example, a globally activated package).
+  ///
+  /// In-memory entrypoints' lockfiles are always considered up-to-date.
+  final bool _inMemory;
+
   /// The lockfile for the entrypoint.
   ///
   /// If not provided to the entrypoint, it will be laoded lazily from disc.
@@ -66,11 +72,13 @@ class Entrypoint {
   Entrypoint(String rootDir, SystemCache cache, {bool packageSymlinks: true})
       : root = new Package.load(null, rootDir, cache.sources),
         cache = cache,
-        _packageSymlinks = packageSymlinks;
+        _packageSymlinks = packageSymlinks,
+        _inMemory = false;
 
   /// Creates an entrypoint given package and lockfile objects.
   Entrypoint.inMemory(this.root, this._lockFile, this.cache)
-      : _packageSymlinks = false;
+      : _packageSymlinks = false,
+        _inMemory = true;
 
   /// The path to the entrypoint's "packages" directory.
   String get packagesDir => root.path('packages');
@@ -562,6 +570,8 @@ class Entrypoint {
   /// contains dependencies that are not in the lockfile or that don't match
   /// what's in there.
   bool _isLockFileUpToDate(LockFile lockFile) {
+    if (_inMemory) return true;
+
     return root.immediateDependencies.every((package) {
       var locked = lockFile.packages[package.name];
       if (locked == null) return false;