Refactor ChooserDialogView to use borders instead of content margins.

chrome/browser/chooser_controller/mock_chooser_controller.cc

Index: chrome/browser/chooser_controller/mock_chooser_controller.cc
diff --git a/chrome/browser/chooser_controller/mock_chooser_controller.cc b/chrome/browser/chooser_controller/mock_chooser_controller.cc
index 9763d8c759ca2d8ef0f670336dae363d3a23faa8..c4632e470e5f4ad3519a4165a88de2830a28b133 100644
--- a/chrome/browser/chooser_controller/mock_chooser_controller.cc
+++ b/chrome/browser/chooser_controller/mock_chooser_controller.cc
@@ -14,7 +14,9 @@
 MockChooserController::MockChooserController()
     : ChooserController(nullptr,
                         IDS_USB_DEVICE_CHOOSER_PROMPT_ORIGIN,

[Jeffrey Yasskin, 2017/06/15 22:06:30]

Note that this superclass constructor call does set the title, just to a
maybe-nonobvious value. You might not need this change at all.

[Bret, 2017/06/15 22:50:14]

Not if the owner pointer is null. I figured setting the title directly was
better than drumming up a mock RenderFrameHost just for that.

-                        IDS_USB_DEVICE_CHOOSER_PROMPT_EXTENSION_NAME) {}
+                        IDS_USB_DEVICE_CHOOSER_PROMPT_EXTENSION_NAME) {
+  set_title(base::ASCIIToUTF16("Mock Chooser Dialog"));
+}
 
 MockChooserController::~MockChooserController() {}