[Mac] Refactor Immersive Fullscreen Logic

ui/base/cocoa/tracking_area.mm

Index: ui/base/cocoa/tracking_area.mm
diff --git a/ui/base/cocoa/tracking_area.mm b/ui/base/cocoa/tracking_area.mm
index e68fb5beae272e417f9e535508abb52ecdace306..f310514d69bfeb4430dd0355e95b6c0b93cb8bb9 100644
--- a/ui/base/cocoa/tracking_area.mm
+++ b/ui/base/cocoa/tracking_area.mm
@@ -101,6 +101,13 @@
                object:window];
 }
 
+- (BOOL)mouseInsideTrackingAreaForView:(NSView*)view {
+  DCHECK(view);
+  NSPoint mouseLoc = [[view window] mouseLocationOutsideOfEventStream];
+  NSPoint mousePos = [view convertPoint:mouseLoc fromView:nil];
+  return NSMouseInRect(mousePos, [self rect], [view isFlipped]);
+}
+
 - (void)windowWillClose:(NSNotification*)notif {
   [self clearOwner];
 }