Bug 195243. Potential hang in typeaheadfind. r=caillon, sr=sspitzer

extensions/typeaheadfind/src/nsTypeAheadFind.cpp

@@ -1330,6 +1330,7 @@ nsTypeAheadFind::FindItNow(nsIPresShell *aPresShell,
     // ======= end-inner-while (go through a single document) ==========
 
     // ---------- Nothing found yet, try next document  -------------
+    PRBool hasTriedFirstDoc = PR_FALSE;
     do {
       // ==== Second inner loop - get another while  ====
       if (NS_SUCCEEDED(docShellEnumerator->HasMoreElements(&hasMoreDocShells))
@@ -1342,11 +1343,15 @@ nsTypeAheadFind::FindItNow(nsIPresShell *aPresShell,
           break;
         }
       }
+      else if (!hasTriedFirstDoc) {  // Avoid potential infinite loop
+        return NS_ERROR_FAILURE;  // No content doc shells
+      }
 
       // Reached last doc shell, loop around back to first doc shell
       rootContentDocShell->GetDocShellEnumerator(nsIDocShellTreeItem::typeContent,
                                                  nsIDocShell::ENUMERATE_FORWARDS,
                                                  getter_AddRefs(docShellEnumerator));
+      hasTriedFirstDoc = PR_TRUE;
     } while (docShellEnumerator);  // ==== end second inner while  ===
 
     PRBool continueLoop = PR_FALSE;