[Mac] Adjust the size, position and color of security indicator divider.

chrome/browser/ui/cocoa/location_bar/security_state_bubble_decoration.mm

Index: chrome/browser/ui/cocoa/location_bar/security_state_bubble_decoration.mm
diff --git a/chrome/browser/ui/cocoa/location_bar/security_state_bubble_decoration.mm b/chrome/browser/ui/cocoa/location_bar/security_state_bubble_decoration.mm
index 2a8efd6d0a80757f4b46226debf7ec729781568f..f3878f1f5b8465edc537281c7fc76aa2f7fb754d 100644
--- a/chrome/browser/ui/cocoa/location_bar/security_state_bubble_decoration.mm
+++ b/chrome/browser/ui/cocoa/location_bar/security_state_bubble_decoration.mm
@@ -32,6 +32,9 @@ namespace {
 // Padding between the label and icon/divider.
 CGFloat kLabelPadding = 4.0;
 
+// Divider height.
+CGFloat kDividerHeight = 16.0;
+
 // Inset for the background.
 const CGFloat kBackgroundYInset = 4.0;
 
@@ -232,15 +235,29 @@ void SecurityStateBubbleDecoration::DrawInFrame(NSRect frame,
 
     // Draw the divider.
     if (state() == DecorationMouseState::NONE && !active()) {
-      const CGFloat divider_x_position =
-          is_rtl ? NSMinX(decoration_frame) + DividerPadding()
-                 : NSMaxX(decoration_frame) - DividerPadding();
       NSBezierPath* line = [NSBezierPath bezierPath];
       [line setLineWidth:line_width];
-      [line moveToPoint:NSMakePoint(divider_x_position,
-                                    NSMinY(decoration_frame))];
-      [line lineToPoint:NSMakePoint(divider_x_position,
-                                    NSMaxY(decoration_frame))];
+      NSPoint divider_origin = NSZeroPoint;
+      divider_origin.x = is_rtl ? NSMinX(decoration_frame) + DividerPadding()
+                                : NSMaxX(decoration_frame) - DividerPadding();
+      // Screen pixels lay between integral coordinates in user space. If you
+      // draw a line from (16, 16) to (16, 32), Core Graphics maps that line to
+      // the pixels that lay along x=16.5. In order to achieve a line that
+      // appears to lay along x=16, CG will perform dithering. To get a crisp
+      // line, you have to specify x=16.5, so translating by 1/2 the 1-pixel
+      // line width creates the crisp line we want. We subtract to better center
+      // the line between the label and URL.
+      divider_origin.x -= line_width / 2.;
+      CGFloat divider_y_frame_offset =
+          (NSHeight(decoration_frame) - kDividerHeight) / 2.0;
+      divider_origin.y = NSMinY(decoration_frame) + divider_y_frame_offset;
+      // Adjust the divider origin by 1/2 a point to visually center the
+      // divider vertically on Retina.
+      if (line_width < 1) {
+        divider_origin.y -= 0.5;
+      }
+      [line moveToPoint:divider_origin];
+      [line relativeLineToPoint:NSMakePoint(0, kDividerHeight)];
 
       NSColor* divider_color = GetDividerColor(in_dark_mode);
       CGFloat divider_alpha =