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

components/autofill/content/browser/content_autofill_driver.cc

Index: components/autofill/content/browser/content_autofill_driver.cc
diff --git a/components/autofill/content/browser/content_autofill_driver.cc b/components/autofill/content/browser/content_autofill_driver.cc
index 65ed75ac269acdc6460028827bce3978674c84da..2b9a108e7549c62036aaf3f35bc536071f23f675 100644
--- a/components/autofill/content/browser/content_autofill_driver.cc
+++ b/components/autofill/content/browser/content_autofill_driver.cc
@@ -20,8 +20,10 @@
 #include "content/public/browser/navigation_details.h"
 #include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/render_view_host.h"
+#include "content/public/browser/render_widget_host_view.h"
 #include "content/public/browser/site_instance.h"
 #include "ipc/ipc_message_macros.h"
+#include "ui/gfx/geometry/size_f.h"
 
 namespace autofill {
 
@@ -147,6 +149,19 @@ void ContentAutofillDriver::PopupHidden() {
     RendererShouldClearPreviewedForm();
 }
 
+gfx::RectF ContentAutofillDriver::TransformBoundingBox(
+    const gfx::RectF& bounding_box) {
+  gfx::Point orig_point(bounding_box.x(), bounding_box.y());
+  gfx::Point transformed_point;
+  render_frame_host_->GetView()->TransformPointToRootCoordSpace(
+      orig_point, &transformed_point);

[kenrb, 2016/01/20 21:38:43]

There is a loss of precision here, is this a real problem?

The gfx::Transform class only operates on Point and Point3_f, not PointF, so
there isn't an easy way to plumb transformation all the way through the hit
testing code for PointF. Accordingly, we are transforming a discrete Point
rather than a PointF, and converting back and forth. It's not clear to me that
this has any noticeable effect on the resulting position of the popup.

[Ilya Sherman, 2016/01/20 23:12:15]

nit: Can TransformPointToRootCoordSpace just return the transformed point? 
That's a slightly simpler API.

[Ilya Sherman, 2016/01/20 23:12:15]

I'm not sure -- I'd recommend checking with someone super familiar with the gfx
system.

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

Done.

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

I talked to vollick@, and he thinks it should be fine since subframes and parent
frames will always have the same zoom level, but says we the values need to be
rounded rather than truncated. Accordingly, I have uploaded a patch that adds a
TransformPointToRootCoordSpaceF API that does this.

+
+  gfx::RectF new_box;
+  new_box.SetRect(transformed_point.x(), transformed_point.y(),
+                  bounding_box.width(), bounding_box.height());
+  return new_box;
+}
+
 bool ContentAutofillDriver::HandleMessage(const IPC::Message& message) {
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(ContentAutofillDriver, message)