Add a "pub dependencies" command.

sdk/lib/_internal/pub/lib/src/utils.dart

Index: sdk/lib/_internal/pub/lib/src/utils.dart
diff --git a/sdk/lib/_internal/pub/lib/src/utils.dart b/sdk/lib/_internal/pub/lib/src/utils.dart
index f5727a46eeff0127eed9ad2d35b11fa6a458ceb3..719b29efbdc767ae27a2b532c6dffd7bc8325cf0 100644
--- a/sdk/lib/_internal/pub/lib/src/utils.dart
+++ b/sdk/lib/_internal/pub/lib/src/utils.dart
@@ -687,9 +687,9 @@ String prefixLines(String text, {String prefix: '| ', String firstPrefix}) {
   return lines.join('\n');
 }
 
-/// Whether pub is running as a subprocess in an integration test.
-bool get runningAsTest =>
-  Platform.environment.containsKey('_PUB_TESTING');
+/// Whether pub is running as a subprocess in an integration test or in a unit
+/// test that has explicitly set this.
+bool runningAsTest = Platform.environment.containsKey('_PUB_TESTING');
 
 /// Wraps [fn] to guard against several different kinds of stack overflow
 /// exceptions: