views: make TabCloseButton a square

Without any stored images, TabCloseButton falls back to the default sizing for
ImageButton, which is 16x14. This change makes it always a square, which makes
the focus ring and ink drop circles instead of ovals.

Bug: 873063
Change-Id: I5c2deec54f768d64be14ee0f9c0adcb52a8d754e
Reviewed-on: https://chromium-review.googlesource.com/1172506Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582903}

chrome/browser/ui/views/tabs/tab_close_button.cc

@@ -119,6 +119,14 @@ void TabCloseButton::Layout() {
   }
 }
 
+gfx::Size TabCloseButton::CalculatePreferredSize() const {
+  int width = GetWidth();
+  gfx::Size size(width, width);
+  gfx::Insets insets = GetInsets();
+  size.Enlarge(insets.width(), insets.height());
+  return size;
+}
+
 void TabCloseButton::PaintButtonContents(gfx::Canvas* canvas) {
   canvas->SaveLayerAlpha(GetOpacity());
   ButtonState button_state = state();

chrome/browser/ui/views/tabs/tab_close_button.h

@@ -49,6 +49,7 @@ class TabCloseButton : public views::ImageButton,
   void OnGestureEvent(ui::GestureEvent* event) override;
   const char* GetClassName() const override;
   void Layout() override;
+  gfx::Size CalculatePreferredSize() const override;
 
  protected:
   void PaintButtonContents(gfx::Canvas* canvas) override;