[mac] In app windows, calculate the window corner radius programmatically.

chrome/browser/ui/cocoa/extensions/shell_window_cocoa.mm

Index: chrome/browser/ui/cocoa/extensions/shell_window_cocoa.mm
diff --git a/chrome/browser/ui/cocoa/extensions/shell_window_cocoa.mm b/chrome/browser/ui/cocoa/extensions/shell_window_cocoa.mm
index 479114c31a81bbb470f150af05ffa3fdd2f05708..0333247d248f19f1915c356b473f273e4a4dbdc9 100644
--- a/chrome/browser/ui/cocoa/extensions/shell_window_cocoa.mm
+++ b/chrome/browser/ui/cocoa/extensions/shell_window_cocoa.mm
@@ -56,16 +56,26 @@
 
 @end
 
+// This is really a method on NSGrayFrame, so it should only be called on the
+// view passed into -[NSWindow drawCustomFrameRect:forView:].
+@interface NSView (PrivateMethods)
+- (CGFloat)roundedCornerRadius;
+@end
+
 @implementation ShellNSWindow
 
 - (void)drawCustomFrameRect:(NSRect)rect forView:(NSView*)view {
   [[NSBezierPath bezierPathWithRect:rect] addClip];
   [[NSColor clearColor] set];
   NSRectFill(rect);
-  const CGFloat kWindowBorderRadius = 3.0;
+
+  // Set up our clip.
+  CGFloat cornerRadius = 4.0;
+  if ([view respondsToSelector:@selector(roundedCornerRadius)])
+    cornerRadius = [view roundedCornerRadius];
   [[NSBezierPath bezierPathWithRoundedRect:[view bounds]
-                                   xRadius:kWindowBorderRadius
-                                   yRadius:kWindowBorderRadius] addClip];
+                                   xRadius:cornerRadius
+                                   yRadius:cornerRadius] addClip];
   [[NSColor whiteColor] set];
   NSRectFill(rect);
 }