Fix non-fatal error in StarlarkProvider.export()

Follow-up to https://github.com/bazelbuild/bazel/commit/859d7faa49c582cf3ed33a2436678a4e853a6a42 - .bzl loading thread exportables' owner
is now BzlLoadThreadOwner, not BzlLoadValue.Key.

We didn't catch this before because StarlarkProvider explicitly
omits the owner check when running under tests.

PiperOrigin-RevId: 964184306
Change-Id: I0e79625c6eaa5f61b6cdeb3529ca3ff2fd2dccc9

src/main/java/com/google/devtools/build/lib/packages/StarlarkProvider.java

diff --git a/src/main/java/com/google/devtools/build/lib/packages/StarlarkProvider.java b/src/main/java/com/google/devtools/build/lib/packages/StarlarkProvider.java
index 19be348..f0934e0 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/StarlarkProvider.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/StarlarkProvider.java
@@ -30,6 +30,7 @@
 import com.google.devtools.build.lib.collect.nestedset.Depset;
 import com.google.devtools.build.lib.collect.nestedset.NestedSet;
 import com.google.devtools.build.lib.events.EventHandler;
+import com.google.devtools.build.lib.skyframe.BzlLoadThreadOwner;
 import com.google.devtools.build.lib.skyframe.BzlLoadValue;
 import com.google.devtools.build.lib.util.Fingerprint;
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
@@ -482,15 +483,15 @@
       EventHandler handler, Label extensionLabel, String exportedName, Location exportedLocation) {
     Preconditions.checkState(!isExported());
     SymbolGenerator.Symbol<?> identifier = (SymbolGenerator.Symbol<?>) keyOrIdentityToken;
-    if (identifier.getOwner() instanceof BzlLoadValue.Key bzlKey) {
+    if (identifier.getOwner() instanceof BzlLoadThreadOwner bzlLoadOwner) {
       // In production code, StarlarkProviders are created only when loading .bzl files so the owner
       // of the Symbol should be a BzlLoadValue.Key.
       checkArgument(
-          extensionLabel.equals(bzlKey.getLabel()),
+          extensionLabel.equals(bzlLoadOwner.key().getLabel()),
           "export extensionLabel=%s, but owner=%s",
           extensionLabel,
-          bzlKey);
-      this.keyOrIdentityToken = new Key(bzlKey, exportedName);
+          bzlLoadOwner.key());
+      this.keyOrIdentityToken = new Key(bzlLoadOwner.key(), exportedName);
     } else {
       // In tests, the symbol may be arbitrary.
       if (!isInTest()) {