Position autofill popup widgets correctly under --site-per-process

content/public/browser/render_widget_host_view.h

Index: content/public/browser/render_widget_host_view.h
diff --git a/content/public/browser/render_widget_host_view.h b/content/public/browser/render_widget_host_view.h
index 9b48ddba29d99835e1c994a8e5c068ad2a7fc9b4..3ac98a2fd41700d38a01517f06ee7739246d6af2 100644
--- a/content/public/browser/render_widget_host_view.h
+++ b/content/public/browser/render_widget_host_view.h
@@ -65,6 +65,14 @@ class CONTENT_EXPORT RenderWidgetHostView {
   // Retrieves the last known scroll position.
   virtual gfx::Vector2dF GetLastScrollOffset() const = 0;
 
+  // If a RenderWidgetHost is dealing with points that are transformed from the
+  // root frame for a page (i.e. because its content is contained within
+  // that of another RenderWidgetHost), this provides a facility to convert

[Charlie Reis, 2016/01/21 00:33:03]

Maybe drop "that of"?

[kenrb, 2016/01/22 18:33:59]

I ended up rewriting to make the whole thing clearer. PTAL.

[Charlie Reis, 2016/01/22 23:04:54]

Acknowledged.

+  // a point from its own coordinate space to that of the root frame.

[Charlie Reis, 2016/01/21 00:33:03]

Is this a no-op if you call it on the root RWHV?  (Maybe mention that.)

[kenrb, 2016/01/22 18:33:58]

Done.

+  virtual void TransformPointToRootCoordSpace(

[Charlie Reis, 2016/01/21 00:33:03]

Sanity check: I don't suppose it would be possible to hide this detail and only
expose transformed points from RenderWidgetHost's APIs?  It seems like we'll be
playing whack-a-mole with all the calls to APIs that expose points until we
transform them all, and we'll likely miss future call sites.

[kenrb, 2016/01/22 18:33:59]

It would be nice if there was a more generic way to do this, but this doesn't
seem feasible when components handle their own IPCs -- the coordinates can't be
transformed in the content layer because content classes cannot see the IPC
message definitions. On the bright side, the renderer sending point coordinates
to the browser process seems to be relatively uncommon.

[Charlie Reis, 2016/01/22 23:04:54]

Ok, we can go with this approach.

+      const gfx::Point& point,
+      gfx::Point* transformed_point) = 0;

[Charlie Reis, 2016/01/21 00:33:03]

+1 to returning the result if possible, rather than having an out parameter.

[kenrb, 2016/01/22 18:33:59]

Done.

+
   // Retrieves the native view used to contain plugins and identify the
   // renderer in IPC messages.
   virtual gfx::NativeView GetNativeView() const = 0;