diff --git a/mozilla/modules/libjar/nsJAR.cpp b/mozilla/modules/libjar/nsJAR.cpp
index 6514d1a45dd..a0bdc2fed09 100644
--- a/mozilla/modules/libjar/nsJAR.cpp
+++ b/mozilla/modules/libjar/nsJAR.cpp
@@ -1096,6 +1096,11 @@ NS_IMPL_THREADSAFE_ISUPPORTS1(nsZipReaderCache, nsIZipReaderCache)
 nsZipReaderCache::nsZipReaderCache()
   : mLock(nsnull),
     mZips(16),
+#ifdef ZIP_CACHE_HIT_RATE
+    mZipCacheLookups(0),
+    mZipCacheHits(0),
+    mZipCacheFlushes(0),
+#endif
     mFreeCount(0)
 {
   NS_INIT_REFCNT();
@@ -1126,6 +1131,12 @@ nsZipReaderCache::~nsZipReaderCache()
   if (mLock)
     PR_DestroyLock(mLock);
   mZips.Enumerate(DropZipReaderCache, nsnull);
+
+#ifdef ZIP_CACHE_HIT_RATE
+  printf("nsZipReaderCache size=%d hits=%d lookups=%d rate=%f%% flushes=%d\n",
+         mZipCacheHits, mZipCacheLookups, (float)mZipCacheHits / mZipCacheLookups,
+         mZipCacheFlushes);
+#endif
 }
 
 NS_METHOD
@@ -1149,6 +1160,10 @@ nsZipReaderCache::GetZip(nsIFile* zipFile, nsIZipReader* *result)
   nsresult rv;
   nsAutoLock lock(mLock);
 
+#ifdef ZIP_CACHE_HIT_RATE
+  mZipCacheLookups++;
+#endif
+
   nsXPIDLCString path;
   rv = zipFile->GetPath(getter_Copies(path));
   if (NS_FAILED(rv)) return rv;
@@ -1156,6 +1171,9 @@ nsZipReaderCache::GetZip(nsIFile* zipFile, nsIZipReader* *result)
   nsCStringKey key(path);
   nsJAR* zip = (nsJAR*)mZips.Get(&key); // AddRefs
   if (zip) {
+#ifdef ZIP_CACHE_HIT_RATE
+    mZipCacheHits++;
+#endif
     if (zip->GetReleaseTime() != PR_INTERVAL_NO_TIMEOUT) {
       // this was an otherwise-free entry, so decrement our free counter
       NS_ASSERTION(mFreeCount > 0, "mFreeCount screwed up");
@@ -1223,6 +1241,10 @@ nsZipReaderCache::ReleaseZip(nsJAR* zip)
   }
   NS_ASSERTION(oldest, "wacked");
 
+#ifdef ZIP_CACHE_HIT_RATE
+    mZipCacheFlushes++;
+#endif
+
   // remove from hashtable
   nsCOMPtr<nsIFile> zipFile;
   rv = oldest->GetFile(getter_AddRefs(zipFile));
diff --git a/mozilla/modules/libjar/nsJAR.h b/mozilla/modules/libjar/nsJAR.h
index 834c9aab85c..9f4fb74d51b 100644
--- a/mozilla/modules/libjar/nsJAR.h
+++ b/mozilla/modules/libjar/nsJAR.h
@@ -171,7 +171,9 @@ protected:
 
 ////////////////////////////////////////////////////////////////////////////////
 
-class nsZipCacheEntry;
+#ifdef DEBUG_warren
+#define ZIP_CACHE_HIT_RATE
+#endif
 
 class nsZipReaderCache : public nsIZipReaderCache
 {
@@ -192,6 +194,13 @@ protected:
   PRInt32               mCacheSize;
   nsSupportsHashtable   mZips;
   PRUint32              mFreeCount;
+
+#ifdef ZIP_CACHE_HIT_RATE
+  PRUint32              mZipCacheLookups;
+  PRUint32              mZipCacheHits;
+  PRUint32              mZipCacheFlushes;
+#endif
+
 };
 
 ////////////////////////////////////////////////////////////////////////////////