Add ctrl+mousewheel plumbing to MimeHandlerView.

Add ctrl+mousewheel plumbing to MimeHandlerView.
This will zoom in/out the view properly.

This CL is dependant on http://crrev.com/597653002

BUG=416332
Test=Load chrome with --enable-mime-handler-view and --out-of-process-pdf
Navigate to a pdf file, Ctrl + wheel up and down should zoom in/out the pdf
properly.

Committed: https://crrev.com/8e78ec069ee92035c1a82817527dd81f448253a1
Cr-Commit-Position: refs/heads/master@{#296455}

[lazyboy, 2014-09-23 18:38:49]

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

[Fady Samuel, 2014-09-23 18:52:12]

https://chromiumcodereview.appspot.com/591243003/diff/1/chrome/browser/guest_...
File
chrome/browser/guest_view/mime_handler_view/chrome_mime_handler_view_guest_delegate.cc
(right):

https://chromiumcodereview.appspot.com/591243003/diff/1/chrome/browser/guest_...
chrome/browser/guest_view/mime_handler_view/chrome_mime_handler_view_guest_delegate.cc:50:
guest_->embedder_web_contents(),
Wow, this is a bit weird. We're telling the embedder to zoom? I'm not sure I
understand what's going on here.

[lazyboy, 2014-09-24 16:26:49]

https://chromiumcodereview.appspot.com/591243003/diff/1/chrome/browser/guest_...
File
chrome/browser/guest_view/mime_handler_view/chrome_mime_handler_view_guest_delegate.cc
(right):

https://chromiumcodereview.appspot.com/591243003/diff/1/chrome/browser/guest_...
chrome/browser/guest_view/mime_handler_view/chrome_mime_handler_view_guest_delegate.cc:50:
guest_->embedder_web_contents(),
On 2014/09/23 18:52:12, Fady Samuel wrote:
> Wow, this is a bit weird. We're telling the embedder to zoom? I'm not sure I
> understand what's going on here.

Hmmm, I tried zooming the guest web_contents first too, which doesn't seem to
work:
1. it zoom only the scroll wheel and the overlay, but not the pdf document
itself.
2. chrome's zoom bookkeeping also gets broken, it keeps showing default zoom
level regardless of how much I zoomed in/out.
Zooming the embedder made everything work here.

[Fady Samuel, 2014-09-24 16:32:21]

https://chromiumcodereview.appspot.com/591243003/diff/1/chrome/browser/guest_...
File
chrome/browser/guest_view/mime_handler_view/chrome_mime_handler_view_guest_delegate.cc
(right):

https://chromiumcodereview.appspot.com/591243003/diff/1/chrome/browser/guest_...
chrome/browser/guest_view/mime_handler_view/chrome_mime_handler_view_guest_delegate.cc:50:
guest_->embedder_web_contents(),
On 2014/09/24 16:26:49, lazyboy wrote:
> On 2014/09/23 18:52:12, Fady Samuel wrote:
> > Wow, this is a bit weird. We're telling the embedder to zoom? I'm not sure I
> > understand what's going on here.
> 
> Hmmm, I tried zooming the guest web_contents first too, which doesn't seem to
> work:
> 1. it zoom only the scroll wheel and the overlay, but not the pdf document
> itself.
> 2. chrome's zoom bookkeeping also gets broken, it keeps showing default zoom
> level regardless of how much I zoomed in/out.
> Zooming the embedder made everything work here.

I guess that makes sense. The guest content in this case is a chrome extension
page and so it's not a part of the tab, and the ZoomController won't see the
zoom changes. If we zoom the embedder, the extension zoom API will see that and
update the guest. LGTM

[lazyboy, 2014-09-24 16:47:55]

The CQ bit was checked by lazyboy@chromium.org

[commit-bot: I haz the power, 2014-09-24 16:49:00]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/591243003/1

[commit-bot: I haz the power, 2014-09-24 17:53:01]

Committed patchset #1 (id:1) as b7215415aec68c4b8fbe52d7b3e2a4cdc25b5f8f

[commit-bot: I haz the power, 2014-09-24 17:53:48]

Patchset 1 (id:??) landed as
https://crrev.com/8e78ec069ee92035c1a82817527dd81f448253a1
Cr-Commit-Position: refs/heads/master@{#296455}