Fix content verification code for undreadable and deleted files.

extensions/browser/content_verify_job.h

Index: extensions/browser/content_verify_job.h
diff --git a/extensions/browser/content_verify_job.h b/extensions/browser/content_verify_job.h
index 15c983ee322fdc1b666f0715115b98c1271f4426..b567ec197da7d08e680d6c43ece3978b76722871 100644
--- a/extensions/browser/content_verify_job.h
+++ b/extensions/browser/content_verify_job.h
@@ -72,6 +72,8 @@ class ContentVerifyJob : public base::RefCountedThreadSafe<ContentVerifyJob> {
 
   class TestDelegate {
    public:
+    virtual ~TestDelegate() {}
+
     // These methods will be called inside BytesRead/DoneReading respectively.
     // If either return something other than NONE, then the failure callback
     // will be dispatched with that reason.