Option-click to download should not display "Save As" UI.

Option-click to download should not display "Save As" UI.

The download manager has a concept of a request originating from the "Save As..." contextual menu v.s. a direct download request from the renderer, however this was't hooked up.

The Download Manager uses boolean variables named "save_as" in various locations to track whether a download originated via a contextual menu selection (in which case the save panel should be displayed) or via a renderer request (in which case no UI should be displayed).

This CL contains 3 distinct changes:

1. DownloadFileManager::OnDownloadURL() is where downloads originating from the contextual menu are dispatched, set save_as to true if the download starts here.

2. ResourceMessageFilter::OnDownloadURL() is where downloads originating from the renderer are dispatched (e.g. option-click), don't display UI for these.

3. The "save_as" variable in the DownloadCreateInfo structure doesn't really reflect the origin of the request but whether the Save panel should be displayed. This can happen for example on a name collision or if the default download location isn't writeable regardless of the action that initiated the download.  Renamed the variable and added documentation to this effect.

BUG=36775
TEST=Option-click an image, the image should be saved without prompting the user for a download locate.  Save an image via the "Save As..." context menu, you should be prompted for the save location.

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=52848

[jeremy, 2010-07-12 11:37:19]

Jay,Evan: Just need a review from one of you :o)

Adam: I'm concerned that there are cases I'm missing where a download originates
from the renderer process, but we should still display the save panel. Can you
think of any?

Note that corner cases such as the default download directory being write
protected are already handled by the download manager.

[Jay Civelli, 2010-07-12 22:51:44]

LGTM

http://codereview.chromium.org/2927006/diff/1/2
File chrome/browser/download/download_file.cc (right):

http://codereview.chromium.org/2927006/diff/1/2#newcode588
chrome/browser/download/download_file.cc:588: bool prompt_for_save_location =
true;
Nit: are you using a local var for commenting purpose? Couldn't you pass true
and comment the parameter instead?