Fix to make the log more meaningful when a user script file of an extension cannot be located

chrome/browser/extensions/user_script_master.cc

 // Copyright (c) 2011 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 "chrome/browser/extensions/user_script_master.h"
 
 #include <string>
 #include <vector>
 
 #include "base/file_path.h"
@@ skipping 146 matching lines @@
 
   // Drop our self-reference.
   // Balances StartLoad().
   Release();
 }
 
 static bool LoadScriptContent(UserScript::File* script_file) {
   std::string content;
   const FilePath& path = ExtensionResource::GetFilePath(
       script_file->extension_root(), script_file->relative_path());
-  if (path.empty() || !file_util::ReadFileToString(path, &content)) {
+  if (path.empty()) {
+    LOG(WARNING) << "Failed to get file path to "
+                 << script_file->relative_path().value() << " from "
+                 << script_file->extension_root().value();
+    return false;
+  }
+  if (!file_util::ReadFileToString(path, &content)) {
     LOG(WARNING) << "Failed to load user script file: " << path.value();
     return false;
   }
 
   // Remove BOM from the content.
   std::string::size_type index = content.find(kUtf8ByteOrderMark);
   if (index == 0) {
     script_file->set_content(content.substr(strlen(kUtf8ByteOrderMark)));
   } else {
     script_file->set_content(content);
@@ skipping 196 matching lines @@
   if (!handle)
     return;
 
   base::SharedMemoryHandle handle_for_process;
   if (!shared_memory->ShareToProcess(handle, &handle_for_process))
     return;  // This can legitimately fail if the renderer asserts at startup.
 
   if (base::SharedMemory::IsHandleValid(handle_for_process))
     process->Send(new ExtensionMsg_UpdateUserScripts(handle_for_process));
 }