Remove two unnecessary params in ViewHostMsg_UpdateRect_Params

Remove two unnecessary params in ViewHostMsg_UpdateRect_Params

scale_factor was not used at all.
scroll_offset was not being used correctly. This CL now grabs the scroll offset from the CompositorFrameMetadata in RenderWidgetHostView.

BUG=none
TBR=kenrb@chromium.org for code deletion in view_messages.h + browser_plugin_messages.h

Committed: https://crrev.com/15c487676ac5c50e1f59461d3c7c3f89cf27838d
Cr-Commit-Position: refs/heads/master@{#292721}

[Fady Samuel, 2014-08-29 21:19:47]

fsamuel@chromium.org changed reviewers:
+ jamesr@chromium.org

[Fady Samuel, 2014-08-29 21:19:48]

James, this is the first cleanup CL of the things we talked about offline.

This CL removes scale_factor and scroll_offset from
ViewHostMsg_UpdateRect_Params.

[jamesr, 2014-08-29 21:32:36]

What process the plugin moves messages?  According to the comment (which may
very well be wrong) the scale factor is used to compute the correct physical
locations for the plugin windows, so we'll want to make sure that computation is
still correct.  Or maybe that comment is wrong and the scale factor wasn't used
for that?

[Fady Samuel, 2014-08-29 21:42:23]

On 2014/08/29 21:32:36, jamesr wrote:
> What process the plugin moves messages?  According to the comment (which may
> very well be wrong) the scale factor is used to compute the correct physical
> locations for the plugin windows, so we'll want to make sure that computation
is
> still correct.  Or maybe that comment is wrong and the scale factor wasn't
used
> for that?

It certainly wasn't hooked up to do anything. The scale factor being passed to
the browser process wasn't being used. Looking at RenderWidgetHostViewBase, it
looks like we use gfx::win::DIPToScreenRect to do the scaling:

https://code.google.com/p/chromium/codesearch#chromium/src/content/browser/re...

[jamesr, 2014-08-29 22:33:06]

OK, so that'll race when the device scale changes.  However, we don't support
dynamic device scale changes on windows (and won't before the end of the year)
and we only support npapi windowed plugins there so it's all fine.

lgtm

[Fady Samuel, 2014-08-29 22:38:09]

The CQ bit was checked by fsamuel@chromium.org

[commit-bot: I haz the power, 2014-08-29 22:43:41]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/fsamuel@chromium.org/525523003/80001

[commit-bot: I haz the power, 2014-08-29 23:53:22]

Committed patchset #5 (id:80001) as 20931556c13c33b771de2b4c43d07a210767db92

[commit-bot: I haz the power, 2014-09-10 03:11:53]

Patchset 5 (id:??) landed as
https://crrev.com/15c487676ac5c50e1f59461d3c7c3f89cf27838d
Cr-Commit-Position: refs/heads/master@{#292721}