Enable url check in download_manager, with a simple UI (it may need polish). The whole thing is still behind a flag.
The download_file_manager will start a url check with safebrowsing. It goes parallel with file creation operation. When url is checked to be dangerous, the UI dialog will show  the dialog. 
TEST=download_manager_unittest
BUG=60822

Review URL: http://codereview.chromium.org/6410050

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@76123 0039d316-1c4b-4281-b951-d872f2087c98
21 files changed