Bug 623813 - Preserve stack traces when rethrowing exceptions conditionally. r=mconnor

services/sync/modules/engines.js

@@ -466,18 +466,13 @@ SyncEngine.prototype = {
       try {
         try {
           item.decrypt();
-        } catch (ex) {
-          if (Utils.isHMACMismatch(ex) &&
-              this.handleHMACMismatch()) {
-            // Let's try handling it.
-            // If the callback returns true, try decrypting again, because
-            // we've got new keys.
-            this._log.info("Trying decrypt again...");
-            item.decrypt();
-          }
-          else {
-            throw ex;
-          }
+        } catch (ex if (Utils.isHMACMismatch(ex) &&
+                        this.handleHMACMismatch())) {
+          // Let's try handling it.
+          // If the callback returns true, try decrypting again, because
+          // we've got new keys.
+          this._log.info("Trying decrypt again...");
+          item.decrypt();
         }
        
         if (this._reconcile(item)) {
@@ -488,14 +483,7 @@ SyncEngine.prototype = {
           count.reconciled++;
           this._log.trace("Skipping reconciled incoming item " + item.id);
         }
-      }
-      catch(ex) {
-
-        if (!Utils.isHMACMismatch(ex)) {
-          // Rethrow anything we shouldn't handle.
-          throw ex;
-        }
-
+      } catch (ex if (Utils.isHMACMismatch(ex))) {
         this._log.warn("Error processing record: " + Utils.exceptionStr(ex));
 
         // Upload a new record to replace the bad one if we have it