Make the header/content separator into a hairline for apps in hidpi

In order to make the hairline header/content separator look good in HiDPI
- The header/content separator overlays the window controls (to avoid a 1 physical pixel gap between the window controls and the header/content separator in 2x)
- This CL makes the window controls 2 physical pixels taller in 2x
- The bottom 1 physical pixel of the window control images is transparent. This is necessary because the window controls paint on top of the header/content separator

BUG=340135
TEST=Manual, see bug
R=jamescook@chromium.org

Review URL: https://codereview.chromium.org/200493004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@258301 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 3 insertions, 4 deletions

diff --git a/ash/frame/header_painter_util.cc b/ash/frame/header_painter_util.cc
index 77123e6..ca83824 100644
--- a/ash/frame/header_painter_util.cc
+++ b/ash/frame/header_painter_util.cc
@@ -74,10 +74,9 @@ gfx::Rect HeaderPainterUtil::GetTitleBounds(
   int x = icon ?
       icon->bounds().right() + kTitleIconOffsetX : kTitleNoIconOffsetX;
   int height = title_font_list.GetHeight();
-  int y = std::max(
-      0,
-      static_cast<int>(std::ceil(
-          (caption_button_container->height() - height) / 2.0f)));
+  // Floor when computing the center of |caption_button_container| and when
+  // computing the center of the text.
+  int y = std::max(0, (caption_button_container->height() / 2) - (height / 2));
   int width = std::max(
       0, caption_button_container->x() - kTitleCaptionButtonSpacing - x);
   return gfx::Rect(x, y, width, height);