BubbleFrameView: add padding if platform dislikes close buttons

ui/views/bubble/bubble_frame_view.cc

Index: ui/views/bubble/bubble_frame_view.cc
diff --git a/ui/views/bubble/bubble_frame_view.cc b/ui/views/bubble/bubble_frame_view.cc
index 43bac842f05e438b5a8001e005c41d2ddc20ddbf..87571234e503adb6176141c993e3750be399707e 100644
--- a/ui/views/bubble/bubble_frame_view.cc
+++ b/ui/views/bubble/bubble_frame_view.cc
@@ -245,7 +245,12 @@ gfx::Insets BubbleFrameView::GetInsets() const {
   const int title_padding = has_title ? title_margins_.height() : 0;
   const int title_height = std::max(icon_height, label_height) + title_padding;
   const int close_height = close_->visible() ? close_->height() : 0;
-  insets += gfx::Insets(std::max(title_height, close_height), 0, 0, 0);
+  const int min_height =
+      !GetWidget()->widget_delegate()->ShouldShowCloseButton()

[msw, 2016/07/28 18:49:32]

This is wrong, numerous cross-platform bubbles and dialogs will override
WidgetDelegate::ShouldShowCloseButton to false:
  https://cs.chromium.org/search/?q=ShouldShowCloseButton.*override
(this will pad unintended bubbles and dialogs like your reverted CL)

Here's my 3-step plan to fix this issue:
(1) Remove the OS_MACOSX exception in WidgetDelegate::ShouldShowCloseButton.
(2) Leave |insets| as it was and change |close_height| to:
  const int close_height =
GetWidget()->widget_delegate()->ShouldShowCloseButton() ? close_->height() : 0;
  insets += gfx::Insets(std::max(title_height, close_height), 0, 0, 0);
(3) Change BubbleFrameView::ResetWindowControls to:
#if defined(OS_MACOSX)
  // The close button is never shown for dialogs or bubbles on Mac.
  close_->SetVisible(false);
#else
  close_->SetVisible(GetWidget()->widget_delegate()->ShouldShowCloseButton());
#endif

This *may* work if I understand the intent correctly. If we *do* want to show
the close button for some Mac dialogs and bubbles, we'll potentially want some
other solution; let's talk more if that's the case, we could possible set some
additional flag, like
|show_padding_instead_of_the_close_button_on_this_mac_dialog| or
|really_actually_show_the_close_button_on_this_mac_dialog|, or devise something
better.

+          ? close_->height()
+          : 0;
+  insets +=
+      gfx::Insets(std::max({title_height, close_height, min_height}), 0, 0, 0);
   return insets;
 }