mac: Pixel-based click detection for the tab close button

chrome/browser/ui/cocoa/hover_close_button.mm

Index: chrome/browser/ui/cocoa/hover_close_button.mm
diff --git a/chrome/browser/ui/cocoa/hover_close_button.mm b/chrome/browser/ui/cocoa/hover_close_button.mm
index 28322b4eae5c3d77c07bd4afa9e906a6a59b680d..f6065af48023ac6833ea8a057052b598fc638358 100644
--- a/chrome/browser/ui/cocoa/hover_close_button.mm
+++ b/chrome/browser/ui/cocoa/hover_close_button.mm
@@ -79,6 +79,22 @@ NSString* const kFadeOutValueKeyPath = @"fadeOutValue";
   [self animationDidStop:animation];
 }
 
+// Override to only accept clicks within the bounds of the defined path, not
+// the entire bounding box. |aPoint| is in the superview's coordinate system.
+- (NSView*)hitTest:(NSPoint)point {
+  NSPoint localPoint = [self convertPoint:point fromView:[self superview]];
+  NSRect pointRect = NSMakeRect(localPoint.x, localPoint.y, 1, 1);
+
+  NSImage* hoverImage = [self imageForHoverState:kHoverStateMouseOver];
+  if ([hoverImage hitTestRect:pointRect
+      withImageDestinationRect:[self bounds]
+                       context:nil
+                         hints:nil
+                       flipped:YES])
+    return [super hitTest:point];
+  return nil;
+}
+
 - (void)drawRect:(NSRect)dirtyRect {
   NSImage* image = [self imageForHoverState:[self hoverState]];