Add ctrl+mousewheel plumbing to MimeHandlerView.

chrome/browser/guest_view/mime_handler_view/chrome_mime_handler_view_guest_delegate.cc

Index: chrome/browser/guest_view/mime_handler_view/chrome_mime_handler_view_guest_delegate.cc
diff --git a/chrome/browser/guest_view/mime_handler_view/chrome_mime_handler_view_guest_delegate.cc b/chrome/browser/guest_view/mime_handler_view/chrome_mime_handler_view_guest_delegate.cc
index 22061509c4633f2b06f2b4922c116600ca30ee9a..46b0952bb67545111e2afabdc1513081ab9acc40 100644
--- a/chrome/browser/guest_view/mime_handler_view/chrome_mime_handler_view_guest_delegate.cc
+++ b/chrome/browser/guest_view/mime_handler_view/chrome_mime_handler_view_guest_delegate.cc
@@ -4,6 +4,7 @@
 
 #include "chrome/browser/guest_view/mime_handler_view/chrome_mime_handler_view_guest_delegate.h"
 
+#include "chrome/browser/chrome_page_zoom.h"
 #include "chrome/browser/ui/pdf/chrome_pdf_web_contents_helper_client.h"
 #include "components/pdf/browser/pdf_web_contents_helper.h"
 #include "extensions/browser/guest_view/mime_handler_view/mime_handler_view_guest.h"
@@ -41,3 +42,11 @@ void ChromeMimeHandlerViewGuestDelegate::AttachHelpers() {
       scoped_ptr<pdf::PDFWebContentsHelperClient>(
           new ChromePDFWebContentsHelperClient()));
 }
+
+void ChromeMimeHandlerViewGuestDelegate::ChangeZoom(bool zoom_in) {
+  // TODO(lazyboy): Move this to //extensions once ZoomController and friends
+  // move to //extensions.
+  chrome_page_zoom::Zoom(
+      guest_->embedder_web_contents(),

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

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]

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]

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

+      zoom_in ? content::PAGE_ZOOM_IN : content::PAGE_ZOOM_OUT);
+}