Implements the "Set to default" button on the zoom bubble.

chrome/browser/ui/views/location_bar/location_bar_view.cc

Index: chrome/browser/ui/views/location_bar/location_bar_view.cc
diff --git a/chrome/browser/ui/views/location_bar/location_bar_view.cc b/chrome/browser/ui/views/location_bar/location_bar_view.cc
index 424f5c5e50ca62297b50c809cf333cb25e92f917..4fbca83c7d8b0c8ccad60f3854651c6303df60f0 100644
--- a/chrome/browser/ui/views/location_bar/location_bar_view.cc
+++ b/chrome/browser/ui/views/location_bar/location_bar_view.cc
@@ -270,7 +270,11 @@ void LocationBarView::Init(views::View* popup_parent_view) {
     content_blocked_view->SetVisible(false);
   }
 
-  zoom_view_ = new ZoomView(model_);
+  // Create the zoom view. At this point, |delegate_| has not yet been assigned
+  // a TabContents, so calling GetTabContents() will just return NULL. Thus,
+  // |delegate_| itself is passed here, where it can be queried at a later time
+  // for the appropriate TabContents.

[Peter Kasting, 2012/07/18 03:26:30]

Nit: This seems a little sketchy since apparently this "assigning" action
happens completely outside our control or visibility -- later we just happily
call GetWebContentsFromDelegate() on the delegate as well as
delegate_->GetTabContents().  Is it possible to make the tab contents be
non-NULL at the time the delegate is passed in to this object so there isn't a
window like this?  If not, is there a specific time where we know the tab
contents will exist so we can e.g. DCHECK that in GetTabContents() and refer to
it in the comments here?

[Kyle Horimoto, 2012/07/18 23:49:38]

Hmm, not exactly. ToolbarView creates a LocationBarView when the window is
created. At this point, we have only created the container (window) for a
TabContents, not the actual TabContents (which is why we can't just call
GetTabContents() here). After the window is set up,
TabStripModel::AppendTabContents() is called with the current tab contents
(e.g., the website being viewed or the NTP). At this point, |delegate_| (which
is the ToolbarView that created the LocationBarView) can get a reference to the
TabContents. Unfortunately, there doesn't seem to be a way to check this except
to DCHECK() that the pointer returned by GetTabContents() is non-NULL :/. Should
I just do that?

+  zoom_view_ = new ZoomView(model_, delegate_);
   AddChildView(zoom_view_);
 
   if (extensions::switch_utils::IsActionBoxEnabled()) {
@@ -515,7 +519,7 @@ void LocationBarView::SetZoomIconState(
 }
 
 void LocationBarView::ShowZoomBubble(int zoom_percent) {

[Peter Kasting, 2012/07/18 03:26:30]

Nit: If this argument is no longer used, can we un-plumb it?

[Kyle Horimoto, 2012/07/18 23:49:38]

This is already being done: http://codereview.chromium.org/10736028/.

-  ZoomBubbleView::ShowBubble(zoom_view_, zoom_percent, true);
+  ZoomBubbleView::ShowBubble(zoom_view_, GetTabContents(), true);
 }
 
 void LocationBarView::ShowChromeToMobileBubble() {