Fix content verification code for undreadable and deleted files.

extensions/browser/content_verify_job.cc

Index: extensions/browser/content_verify_job.cc
diff --git a/extensions/browser/content_verify_job.cc b/extensions/browser/content_verify_job.cc
index e2f9f7eb9c84e0853eed096ae2656c1b6e442d47..8d9ce1aed42333f659e89a9311a3e37ab0e224ba 100644
--- a/extensions/browser/content_verify_job.cc
+++ b/extensions/browser/content_verify_job.cc
@@ -143,8 +143,13 @@ void ContentVerifyJob::DoneReading() {
 }
 
 bool ContentVerifyJob::FinishBlock() {
-  if (current_hash_byte_count_ <= 0)
+  if (!done_reading_ && current_hash_byte_count_ == 0)
     return true;
+  if (!current_hash_) {
+    // This happens when we fail to read the resource. Compute empty content's
+    // hash in this case.
+    current_hash_ = crypto::SecureHash::Create(crypto::SecureHash::SHA256);
+  }
   std::string final(crypto::kSHA256Length, 0);
   current_hash_->Finish(base::string_as_array(& final), final.size());
   current_hash_.reset();