content: Rename webkit_test_helpers.{cc,h} to blink_test_helpers.{cc,h}

Now that webkit/ is gone, we are preparing ourselves for the merge of
third_party/WebKit into //blink.

BUG=None
BUG=content_shell && content_unittests
R=avi@chromium.org

Review URL: https://codereview.chromium.org/1118183003

Cr-Commit-Position: refs/heads/master@{#328202}
void ShellContentBrowserClient::PreSpawnRenderer(sandbox::TargetPolicy* policy,
                                                 bool* success) {
  std::vector<std::string> font_files = GetSideloadFontFiles();
  for (std::vector<std::string>::const_iterator i(font_files.begin());
      i != font_files.end();
      ++i) {
    policy->AddRule(sandbox::TargetPolicy::SUBSYS_FILES,
        sandbox::TargetPolicy::FILES_ALLOW_READONLY,
        base::UTF8ToWide(*i).c_str());
  }
}

void ShellContentBrowserClient::PreSpawnRenderer(sandbox::TargetPolicy* policy,
                                                 bool* success) {
  std::vector<std::string> font_files = GetSideloadFontFiles();
  for (std::vector<std::string>::const_iterator i(font_files.begin());
      i != font_files.end();
      ++i) {
    policy->AddRule(sandbox::TargetPolicy::SUBSYS_FILES,
        sandbox::TargetPolicy::FILES_ALLOW_READONLY,
        base::UTF8ToWide(*i).c_str());
  }
}
