Only perform one read of the hashCode field in our benign-data-racy hashCode() implementation. See http://jeremymanson.blogspot.com/2008/12/benign-data-races-in-java.html.

--
MOS_MIGRATED_REVID=101490349

src/main/java/com/google/devtools/build/skyframe/SkyKey.java

diff --git a/src/main/java/com/google/devtools/build/skyframe/SkyKey.java b/src/main/java/com/google/devtools/build/skyframe/SkyKey.java
index 6916e66..79af14f 100644
--- a/src/main/java/com/google/devtools/build/skyframe/SkyKey.java
+++ b/src/main/java/com/google/devtools/build/skyframe/SkyKey.java
@@ -79,10 +79,12 @@
     // All three of these issues are benign from a correctness perspective; in the end we have no
     // overhead from synchronization, at the cost of potentially computing the hash code more than
     // once.
-    if (hashCode == 0) {
-      hashCode = computeHashCode();
+    int h = hashCode;
+    if (h == 0) {
+      h = computeHashCode();
+      hashCode = h;
     }
-    return hashCode;
+    return h;
   }
 
   private int computeHashCode() {