If ":" is omitted, use same name for package and script in pub global run.

sdk/lib/_internal/pub/test/global/run/implicit_executable_name_test.dart

Index: sdk/lib/_internal/pub/test/global/run/implicit_executable_name_test.dart
diff --git a/sdk/lib/_internal/pub/test/global/run/runs_script_test.dart b/sdk/lib/_internal/pub/test/global/run/implicit_executable_name_test.dart
similarity index 72%
copy from sdk/lib/_internal/pub/test/global/run/runs_script_test.dart
copy to sdk/lib/_internal/pub/test/global/run/implicit_executable_name_test.dart
index 217758f26c34cecdc342d1cf6ecf6a42178e0d30..ad93bac7e2e8e346542b8c95f68b77347f1d4bd6 100644
--- a/sdk/lib/_internal/pub/test/global/run/runs_script_test.dart
+++ b/sdk/lib/_internal/pub/test/global/run/implicit_executable_name_test.dart
@@ -8,19 +8,19 @@ import '../../test_pub.dart';
 
 main() {
   initConfig();
-  integration('runs a script in an activated package', () {
+  integration('defaults to the package name if the script is omitted', () {
     servePackages([
       packageMap("foo", "1.0.0")
     ], contents: [
       d.dir("bin", [
-        d.file("script.dart", "main(args) => print('ok');")
+        d.file("foo.dart", "main(args) => print('foo');")
       ])
     ]);
 
     schedulePub(args: ["global", "activate", "foo"]);
 
-    var pub = pubRun(global: true, args: ["foo", "script"]);
-    pub.stdout.expect("ok");
+    var pub = pubRun(global: true, args: ["foo"]);
+    pub.stdout.expect("foo");
     pub.shouldExit();
   });
 }