Refactor ChooserDialogView to use borders instead of content margins.

chrome/browser/chooser_controller/chooser_controller.h

Index: chrome/browser/chooser_controller/chooser_controller.h
diff --git a/chrome/browser/chooser_controller/chooser_controller.h b/chrome/browser/chooser_controller/chooser_controller.h
index 33658c6ee8e405e567eb169f751bb35c030b7af3..0445af95ca0a73bddc9fd2391a3d2b44ab1d8da1 100644
--- a/chrome/browser/chooser_controller/chooser_controller.h
+++ b/chrome/browser/chooser_controller/chooser_controller.h
@@ -62,7 +62,7 @@ class ChooserController {
   };
 
   // Returns the text to be displayed in the chooser title.
-  base::string16 GetTitle() const;
+  virtual base::string16 GetTitle() const;

[Jeffrey Yasskin, 2017/06/15 21:33:42]

I'm a little unhappy with making this configurable by subclasses, while still
providing the default implementation with a member variable in the base here.
Why do subclasses need to customize this?

[Bret, 2017/06/15 21:54:42]

It's so that MockChooserController can have a title for the browser test. But
you're right, it's a bit wonky. I changed it to a protected set_title method,
what do you think?

 
   // Returns if the chooser needs to show an icon before the text.
   // For WebBluetooth, it is a signal strength icon.