Fix content verification code for undreadable and deleted files.

extensions/browser/extension_protocols.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "extensions/browser/extension_protocols.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 219 matching lines @@
     // TODO(asargent) - we'll need to add proper support for range headers.
     // crbug.com/369895.
     std::string range_header;
     if (headers.GetHeader(net::HttpRequestHeaders::kRange, &range_header)) {
       if (verify_job_.get())
         verify_job_ = NULL;
     }
     URLRequestFileJob::SetExtraRequestHeaders(headers);
   }
 
+  void OnOpenComplete(int result) override {
+    if (result < 0) {
+      // File open failure. |result| is net:: error code.

[Devlin, 2017/03/24 18:50:09]

Let's expand on this a bit - something like:
// This can happen when the file is unreadable (which can happen during
// corruption or third-party interaction), or when the file itself is
// empty. In both of these cases, we need to be sure to inform the
// verification job that we've finished reading so that it can proceed;
// see crbug.com/nnn.

[lazyboy, 2017/03/24 19:22:55]

Done.
The empty case is crbug.com/703892, which is a bug in URLRequestFileJob.

+      if (verify_job_.get()) {
+        std::string tmp;
+        verify_job_->BytesRead(0, base::string_as_array(&tmp));
+        verify_job_->DoneReading();
+      }
+    }
+  }
+
   void OnSeekComplete(int64_t result) override {
     DCHECK_EQ(seek_position_, 0);
     seek_position_ = result;
     // TODO(asargent) - we'll need to add proper support for range headers.
     // crbug.com/369895.
     if (result > 0 && verify_job_.get())
       verify_job_ = NULL;
   }
 
   void OnReadComplete(net::IOBuffer* buffer, int result) override {
@@ skipping 347 matching lines @@
                                extensions::InfoMap* extension_info_map) {
   return base::MakeUnique<ExtensionProtocolHandler>(is_incognito,
                                                     extension_info_map);
 }
 
 void SetExtensionProtocolTestHandler(ExtensionProtocolTestHandler* handler) {
   g_test_handler = handler;
 }
 
 }  // namespace extensions