[Mac][Material Design] Rework how location bar shadow is drawn.

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

Index: chrome/browser/ui/cocoa/location_bar/autocomplete_text_field_cell.mm
diff --git a/chrome/browser/ui/cocoa/location_bar/autocomplete_text_field_cell.mm b/chrome/browser/ui/cocoa/location_bar/autocomplete_text_field_cell.mm
index 2bc741b3aae4ee02b7c3d3064189d7b71cd9dbb5..b9fb37381f6f4b8b427c7e0086b2d180edae3fce 100644
--- a/chrome/browser/ui/cocoa/location_bar/autocomplete_text_field_cell.mm
+++ b/chrome/browser/ui/cocoa/location_bar/autocomplete_text_field_cell.mm
@@ -317,10 +317,6 @@ size_t CalculatePositionsInFrame(
 
   // Compute the border's bezier path.
   NSRect pathRect = NSInsetRect(frame, insetSize, insetSize);
-  // In dark mode, make room for a shadow beneath the bottom edge.
-  if (inDarkMode && isModeMaterial) {
-    pathRect.size.height -= singlePixelLineWidth_;
-  }
   NSBezierPath* path =
       [NSBezierPath bezierPathWithRoundedRect:pathRect
                                       xRadius:kCornerRadius
@@ -369,7 +365,7 @@ size_t CalculatePositionsInFrame(
       }
 
       // Draw a highlight beneath the top edge, and a shadow beneath the bottom
-      // edge.
+      // edge when on a Retina screen.
       {
         gfx::ScopedNSGraphicsContextSaveGState saveState;
         [NSBezierPath setDefaultLineWidth:singlePixelLineWidth_];
@@ -383,10 +379,12 @@ size_t CalculatePositionsInFrame(
         [NSBezierPath strokeLineFromPoint:origin
                                   toPoint:destination];
 
-        origin.y = destination.y = NSMaxY(pathRect) + singlePixelLineWidth_;
-        [[NSColor colorWithCalibratedWhite:69 / 255. alpha:1] set];
-        [NSBezierPath strokeLineFromPoint:origin
-                                  toPoint:destination];
+        if (singlePixelLineWidth_ < 1) {
+          origin.y = destination.y = NSMaxY(pathRect) + singlePixelLineWidth_;
+          [[NSColor colorWithCalibratedWhite:69 / 255. alpha:1] set];

[tapted, 2016/04/22 01:11:46]

This `69` needs to be a constant accessible from a header somewhere.

I'd maybe go all the way to something like

const SkColor kOmniboxSomethingShadowColor = 0xFF454545;

But since other stuff is using `colorWithCalibratedWhite` and I'm scared to
change it, perhaps 

static NSColor* OmniboxViewMac::ShadowColor()

(there is already an OmniboxViewMac::SuggestTextColor()).. and a `static`
OmniboxViewMac::BaseTextColor . bleh - they should both be static)

[shrike, 2016/04/22 02:09:00]

You mention OmniboxViewMac - you aren't saying I need to stick this color in
there? This color/shadow is a bit of polish that's only used in the textfield
cell. The color does appear (now) in two places so I agree it needs to be
defined in one. I think a function makes sense.

[tapted, 2016/04/22 04:41:34]

OmniboxViewMac is the C++ wrapper around the AutocompleteTextField, and it
already has some utility functions like what we are after. But I'm not really
too fussed where the constant is declared, just so long as it's shared.

[shrike, 2016/04/26 19:19:30]

Done.

+          [NSBezierPath strokeLineFromPoint:origin
+                                    toPoint:destination];
+        }
       }
     }
   } else {