cocoa: draw new tab button with heavier stroke in high contrast

chrome/browser/ui/cocoa/new_tab_button.mm

Index: chrome/browser/ui/cocoa/new_tab_button.mm
diff --git a/chrome/browser/ui/cocoa/new_tab_button.mm b/chrome/browser/ui/cocoa/new_tab_button.mm
index 3224e675066a5b43bfe63928b6a36589320d1415..97b3414f29a3251f6c5054192a43c633ff75c30c 100644
--- a/chrome/browser/ui/cocoa/new_tab_button.mm
+++ b/chrome/browser/ui/cocoa/new_tab_button.mm
@@ -32,6 +32,7 @@
 const CGFloat k10PercentAlpha = 0.1;
 const CGFloat k20PercentAlpha = 0.2;
 const CGFloat k25PercentAlpha = 0.25;
+const CGFloat k100PercentAlpha = 1.0;
 
 NSImage* GetMaskImageFromCell(NewTabButtonCell* aCell) {
   return [aCell imageForState:image_button_cell::kDefaultState view:nil];
@@ -185,8 +186,17 @@ - (NSImage*)imageForState:(image_button_cell::ButtonState)state
 // Returns a new tab button image bezier path with the specified line width.
 + (NSBezierPath*)newTabButtonBezierPathWithLineWidth:(CGFloat)lineWidth;
 
-// NSCustomImageRep custom drawing method that renders the new tab button image.
-+ (void)drawNewTabButtonImage:(NewTabButtonCustomImageRep*)imageRep;
+// Draws the new tab button image to |imageRep|, with either a normal stroke or
+// a heavy stroke for increased visibility.
++ (void)drawNewTabButtonImage:(NewTabButtonCustomImageRep*)imageRep
+              withHeavyStroke:(BOOL)heavyStroke;
+
+// NSCustomImageRep custom drawing method shims for normal and heavy strokes
+// respectively.
++ (void)drawNewTabButtonImageWithNormalStroke:
+    (NewTabButtonCustomImageRep*)imageRep;
++ (void)drawNewTabButtonImageWithHeavyStroke:
+    (NewTabButtonCustomImageRep*)imageRep;
 
 // Returns a new tab button image filled with |fillColor|.
 - (NSImage*)imageWithFillColor:(NSColor*)fillColor;
@@ -318,9 +328,13 @@ - (NSImage*)imageForState:(image_button_cell::ButtonState)state
       NOTREACHED();
   }
 
+  SEL drawSelector = @selector(drawNewTabButtonImageWithNormalStroke:);
+  if (theme && theme->ShouldIncreaseContrast())
+    drawSelector = @selector(drawNewTabButtonImageWithHeavyStroke:);
+
   base::scoped_nsobject<NewTabButtonCustomImageRep> imageRep(
       [[NewTabButtonCustomImageRep alloc]
-          initWithDrawSelector:@selector(drawNewTabButtonImage:)
+          initWithDrawSelector:drawSelector
                       delegate:[NewTabButton class]]);
   [imageRep setDestView:self];
   [imageRep setFillColor:fillColor];
@@ -398,7 +412,8 @@ + (NSBezierPath*)newTabButtonBezierPathWithLineWidth:(CGFloat)lineWidth {
   return bezierPath;
 }
 
-+ (void)drawNewTabButtonImage:(NewTabButtonCustomImageRep*)imageRep {
++ (void)drawNewTabButtonImage:(NewTabButtonCustomImageRep*)imageRep
+              withHeavyStroke:(BOOL)heavyStroke {
   [[NSGraphicsContext currentContext]
       cr_setPatternPhase:[imageRep patternPhasePosition]
       forView:[imageRep destView]];
@@ -414,8 +429,9 @@ + (void)drawNewTabButtonImage:(NewTabButtonCustomImageRep*)imageRep {
     [bezierPath fill];
   }
 
+  CGFloat alpha = heavyStroke ? k100PercentAlpha : k25PercentAlpha;
   static NSColor* strokeColor =
-      [[NSColor colorWithCalibratedWhite:0 alpha:k25PercentAlpha] retain];
+      [[NSColor colorWithCalibratedWhite:0 alpha:alpha] retain];
   [strokeColor set];
   [bezierPath stroke];
 
@@ -485,6 +501,16 @@ + (void)drawNewTabButtonImage:(NewTabButtonCustomImageRep*)imageRep {
   }
 }
 
++ (void)drawNewTabButtonImageWithNormalStroke:
+    (NewTabButtonCustomImageRep*)image {
+  [self drawNewTabButtonImage:image withHeavyStroke:NO];
+}
+
++ (void)drawNewTabButtonImageWithHeavyStroke:
+    (NewTabButtonCustomImageRep*)image {
+  [self drawNewTabButtonImage:image withHeavyStroke:YES];
+}
+
 - (NSImage*)imageWithFillColor:(NSColor*)fillColor {
   NSImage* image =
       [[[NSImage alloc] initWithSize:newTabButtonImageSize] autorelease];