Remove FilesToRunProvider.label.

The TransitiveInfoProvider already contains a label, use that instead.

--
MOS_MIGRATED_REVID=120443298
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/FilesToRunProvider.java b/src/main/java/com/google/devtools/build/lib/analysis/FilesToRunProvider.java
index 2dab4b3..35c0b9a 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/FilesToRunProvider.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/FilesToRunProvider.java
@@ -18,7 +18,6 @@
 import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.actions.EmptyRunfilesSupplier;
 import com.google.devtools.build.lib.actions.RunfilesSupplier;
-import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
@@ -34,14 +33,15 @@
   /** The name of the field in Skylark used to access this class. */
   public static final String SKYLARK_NAME = "files_to_run";
 
-  private final Label label;
+  public static final FilesToRunProvider EMPTY =
+      new FilesToRunProvider(ImmutableList.<Artifact>of(), null, null);
+
   private final ImmutableList<Artifact> filesToRun;
   @Nullable private final RunfilesSupport runfilesSupport;
   @Nullable private final Artifact executable;
 
-  public FilesToRunProvider(Label label, ImmutableList<Artifact> filesToRun,
+  public FilesToRunProvider(ImmutableList<Artifact> filesToRun,
       @Nullable RunfilesSupport runfilesSupport, @Nullable Artifact executable) {
-    this.label = label;
     this.filesToRun = filesToRun;
     this.runfilesSupport = runfilesSupport;
     this.executable  = executable;
@@ -50,17 +50,8 @@
   /**
    * Creates an instance that contains one single executable and no other files.
    */
-  public static FilesToRunProvider fromSingleArtifact(Label label, Artifact artifact) {
-    return new FilesToRunProvider(label, ImmutableList.of(artifact), null, artifact);
-  }
-
-  /**
-   * Returns the label that is associated with this piece of information.
-   *
-   * <p>This is usually the label of the target that provides the information.
-   */
-  public Label getLabel() {
-    return label;
+  public static FilesToRunProvider fromSingleExecutableArtifact(Artifact artifact) {
+    return new FilesToRunProvider(ImmutableList.of(artifact), null, artifact);
   }
 
   /**