Mac: Fix rounded corners on browser windows on retina display.

chrome/browser/ui/cocoa/fast_resize_view.mm

Index: chrome/browser/ui/cocoa/fast_resize_view.mm
diff --git a/chrome/browser/ui/cocoa/fast_resize_view.mm b/chrome/browser/ui/cocoa/fast_resize_view.mm
index f4ea8d380b6d794b0f556f4fe3ba0a594f532af4..848d356540a9b42c2e3e8eb3d971dc3c20b18701 100644
--- a/chrome/browser/ui/cocoa/fast_resize_view.mm
+++ b/chrome/browser/ui/cocoa/fast_resize_view.mm
@@ -12,11 +12,26 @@
 #include "ui/base/cocoa/animation_utils.h"
 #include "ui/base/ui_base_switches.h"
 
+namespace {
+
+// The radius of the rounded corners.
+const CGFloat kRoundedCornerRadius = 4;
+
+}  // namespace
+
 @interface FastResizeView (PrivateMethods)
 // Lays out this views subviews.  If fast resize mode is on, does not resize any
 // subviews and instead pegs them to the top left.  If fast resize mode is off,
 // sets the subviews' frame to be equal to this view's bounds.
 - (void)layoutSubviews;
+
+// Creates a path whose bottom two corners are rounded.
+// Caller takes ownership of the path.
+- (CGPathRef)createRoundedBottomCornersPath:(NSSize)size;
+
+// Updates the path of the layer mask to reflect the current value of
+// roundedBottomCorners_ and fastResizeMode_.
+- (void)updateLayerMask;
 @end
 
 @implementation FastResizeView
@@ -30,6 +45,9 @@
       [layer setBackgroundColor:CGColorGetConstantColor(kCGColorWhite)];
       [self setLayer:layer];
       [self setWantsLayer:YES];
+
+      roundedBottomCorners_ = YES;
+      [self updateLayerMask];
     }
   }
   return self;
@@ -44,6 +62,7 @@
     return;
 
   fastResizeMode_ = fastResizeMode;
+  [self updateLayerMask];
 
   // Force a relayout when coming out of fast resize mode.
   if (!fastResizeMode_)
@@ -52,6 +71,14 @@
   [self setNeedsDisplay:YES];
 }
 
+- (void)setRoundedBottomCorners:(BOOL)roundedBottomCorners {
+  if (roundedBottomCorners == roundedBottomCorners_)
+    return;
+
+  roundedBottomCorners_ = roundedBottomCorners;
+  [self updateLayerMask];
+}
+
 - (void)resizeSubviewsWithOldSize:(NSSize)oldSize {
   [self layoutSubviews];
 }
@@ -67,6 +94,12 @@
   NSRectFill(dirtyRect);
 }
 
+// Every time the frame's size changes, the layer mask needs to be updated.
+- (void)setFrameSize:(NSSize)newSize {
+  [super setFrameSize:newSize];
+  [self updateLayerMask];
+}
+
 @end
 
 @implementation FastResizeView (PrivateMethods)
@@ -93,4 +126,59 @@
   }
 }
 
+- (CGPathRef)createRoundedBottomCornersPath:(NSSize)size {
+  CGMutablePathRef path = CGPathCreateMutable();
+  CGFloat width = size.width;
+  CGFloat height = size.height;
+  CGFloat cornerRadius = kRoundedCornerRadius;
+
+  // Top left corner.
+  CGPathMoveToPoint(path, NULL, 0, height);
+
+  // Top right corner.
+  CGPathAddLineToPoint(path, NULL, width, height);
+
+  // Bottom right corner.
+  CGPathAddArc(path,
+               NULL,
+               width - cornerRadius,
+               cornerRadius,
+               cornerRadius,
+               0,
+               -M_PI_2,
+               true);
+
+  // Bottom left corner.
+  CGPathAddArc(path,
+               NULL,
+               cornerRadius,
+               cornerRadius,
+               cornerRadius,
+               -M_PI_2,
+               -M_PI,
+               true);
+
+  // Draw line back to top-left corner.
+  CGPathAddLineToPoint(path, NULL, 0, height);
+  CGPathCloseSubpath(path);
+  return path;
+}
+
+- (void)updateLayerMask {
+  if (fastResizeMode_ || !roundedBottomCorners_) {
+    [self layer].mask = nil;
+    layerMask_ = nil;
+    return;
+  }
+
+  if (![self layer].mask) {
+    layerMask_ = [CAShapeLayer layer];
+    [self layer].mask = layerMask_;
+  }
+
+  CGPathRef path = [self createRoundedBottomCornersPath:self.bounds.size];
+  layerMask_.path = path;
+  CGPathRelease(path);
+}
+
 @end