Code: void WallpaperManager::OnWallpaperDecoded(
    const AccountId& account_id,
    const wallpaper::WallpaperInfo& info,
    bool update_wallpaper,
    MovableOnDestroyCallbackHolder on_finish,
    std::unique_ptr<user_manager::UserImage> user_image) {
  DCHECK_CURRENTLY_ON(BrowserThread::UI);
  TRACE_EVENT_ASYNC_END0("ui", "LoadAndDecodeWallpaper", this);

  if (user_image->image().isNull()) {
    wallpaper::WallpaperInfo default_info(
         "", wallpaper::WALLPAPER_LAYOUT_CENTER_CROPPED, wallpaper::DEFAULT,
         base::Time::Now().LocalMidnight());
     SetUserWallpaperInfo(account_id, default_info, true);
    if (update_wallpaper)
      DoSetDefaultWallpaper(account_id, std::move(on_finish));
     return;
   }
 
  wallpaper_cache_[account_id].second = user_image->image();

  if (update_wallpaper)
    SetWallpaper(user_image->image(), info);
}

Vulnerability Type: XSS +Info 
CWE ID: CWE-200
Summary: The XSSAuditor::canonicalize function in core/html/parser/XSSAuditor.cpp in the XSS auditor in Blink, as used in Google Chrome before 44.0.2403.89, does not properly choose a truncation point, which makes it easier for remote attackers to obtain sensitive information via an unspecified linear-time attack.
Commit Message: [reland] Do not set default wallpaper unless it should do so.

TBR=bshe@chromium.org, alemate@chromium.org

Bug: 751382
Change-Id: Id0793dfe467f737526a95b1e66ed01fbb8860bda
Reviewed-on: https://chromium-review.googlesource.com/619754
Commit-Queue: Xiaoqian Dai <xdai@chromium.org>
Reviewed-by: Alexander Alekseev <alemate@chromium.org>
Reviewed-by: Biao She <bshe@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#498325}
Reviewed-on: https://chromium-review.googlesource.com/646430
Cr-Commit-Position: refs/heads/master@{#498982}