The close button for bubbles should be an ImageButton, not a LabelButton.

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 c22d511771c21b1b10e67ae4e89b91b281ee2adc..d27aa9d253f7b0d796eaeb133668c989600bfb06 100644
--- a/ui/views/bubble/bubble_frame_view.cc
+++ b/ui/views/bubble/bubble_frame_view.cc
@@ -25,9 +25,9 @@
 #include "ui/resources/grit/ui_resources.h"
 #include "ui/strings/grit/ui_strings.h"
 #include "ui/views/bubble/bubble_border.h"
-#include "ui/views/controls/button/label_button.h"
 #include "ui/views/controls/button/vector_icon_button.h"
 #include "ui/views/controls/image_view.h"
+#include "ui/views/controls/label.h"
 #include "ui/views/layout/box_layout.h"
 #include "ui/views/layout/layout_constants.h"
 #include "ui/views/resources/grit/views_resources.h"
@@ -46,7 +46,7 @@ const SkColor kFootnoteBackgroundColor = SkColorSetRGB(245, 245, 245);
 const SkColor kFootnoteBorderColor = SkColorSetRGB(229, 229, 229);
 
 constexpr int kClosePaddingRight = 7;
-constexpr int kClosePaddingTop = 6;
+constexpr int kClosePaddingTop = 7;
 
 // The MD spec states that the center of the "x" should be 16x16 from the top
 // right of the dialog.
@@ -116,26 +116,25 @@ BubbleFrameView::~BubbleFrameView() {}
 
 // static
 Button* BubbleFrameView::CreateCloseButton(VectorIconButtonDelegate* delegate) {
-  Button* close_button = nullptr;
+  ImageButton* close_button = nullptr;
   if (ui::MaterialDesignController::IsSecondaryUiMaterial()) {
     VectorIconButton* close = new VectorIconButton(delegate);
     close->SetIcon(gfx::VectorIconId::BAR_CLOSE);
-    close->SetSize(close->GetPreferredSize());
     close_button = close;
   } else {
-    ui::ResourceBundle& rb = ui::ResourceBundle::GetSharedInstance();
-    LabelButton* close = new LabelButton(delegate, base::string16());
-    close->SetImage(CustomButton::STATE_NORMAL,
-                    *rb.GetImageNamed(IDR_CLOSE_DIALOG).ToImageSkia());
-    close->SetImage(CustomButton::STATE_HOVERED,
-                    *rb.GetImageNamed(IDR_CLOSE_DIALOG_H).ToImageSkia());
-    close->SetImage(CustomButton::STATE_PRESSED,
-                    *rb.GetImageNamed(IDR_CLOSE_DIALOG_P).ToImageSkia());
-    close->SetBorder(nullptr);
-    close->SetSize(close->GetPreferredSize());
-    close_button = close;
+    ui::ResourceBundle* rb = &ui::ResourceBundle::GetSharedInstance();
+    close_button = new ImageButton(delegate);
+    close_button->SetImage(CustomButton::STATE_NORMAL,
+                           *rb->GetImageNamed(IDR_CLOSE_DIALOG).ToImageSkia());
+    close_button->SetImage(
+        CustomButton::STATE_HOVERED,
+        *rb->GetImageNamed(IDR_CLOSE_DIALOG_H).ToImageSkia());
+    close_button->SetImage(
+        CustomButton::STATE_PRESSED,
+        *rb->GetImageNamed(IDR_CLOSE_DIALOG_P).ToImageSkia());
   }
   close_button->SetTooltipText(l10n_util::GetStringUTF16(IDS_APP_CLOSE));
+  close_button->SizeToPreferredSize();
   return close_button;
 }
 
@@ -315,13 +314,14 @@ void BubbleFrameView::Layout() {
   // there's no title.
   DCHECK(!title_margins_.IsEmpty() || !title_->visible());
 
-  gfx::Rect bounds(GetContentsBounds());
+  const gfx::Rect contents_bounds = GetContentsBounds();
+  gfx::Rect bounds = contents_bounds;
   bounds.Inset(title_margins_);
   if (bounds.IsEmpty())
     return;
 
   // The close button is positioned somewhat closer to the edge of the bubble.
-  gfx::Point close_position = GetContentsBounds().top_right();
+  gfx::Point close_position = contents_bounds.top_right();
   if (ui::MaterialDesignController::IsSecondaryUiMaterial()) {

[msw, 2017/01/31 17:53:16]

q: did you remember to test MD and non-MD?

[Peter Kasting, 2017/01/31 21:31:01]

The Harmony close button is a VectorIconButton instead, so it's not actually
affected by this change.

     close_position += gfx::Vector2d(-close_->width() - kClosePaddingRightMd,
                                     kClosePaddingTopMd);
@@ -353,11 +353,10 @@ void BubbleFrameView::Layout() {
   bounds.set_height(title_height);
 
   if (footnote_container_) {
-    gfx::Rect local_bounds = GetContentsBounds();
-    int height = footnote_container_->GetHeightForWidth(local_bounds.width());
-    footnote_container_->SetBounds(local_bounds.x(),
-                                   local_bounds.bottom() - height,
-                                   local_bounds.width(), height);
+    const int width = contents_bounds.width();
+    const int height = footnote_container_->GetHeightForWidth(width);
+    footnote_container_->SetBounds(
+        contents_bounds.x(), contents_bounds.bottom() - height, width, height);
   }
 }