feat: implement will-move event on macOS

docs/api/browser-window.md

@@ -516,14 +516,14 @@ Note that this is only emitted when the window is being resized manually. Resizi
 
 Emitted after the window has been resized.
 
-#### Event: 'will-move' _Windows_
+#### Event: 'will-move' _macOS_ _Windows_
 
 Returns:
 
 * `event` Event
 * `newBounds` [`Rectangle`](structures/rectangle.md) - Location the window is being moved to.
 
-Emitted before the window is moved. Calling `event.preventDefault()` will prevent the window from being moved.
+Emitted before the window is moved. On Windows, calling `event.preventDefault()` will prevent the window from being moved.
 
 Note that this is only emitted when the window is being resized manually. Resizing the window with `setBounds`/`setSize` will not emit this event.
 

shell/browser/ui/cocoa/atom_ns_window_delegate.mm

@@ -138,6 +138,16 @@ - (void)windowDidResize:(NSNotification*)notification {
   shell_->NotifyWindowResize();
 }
 
+- (void)windowWillMove:(NSNotification*)notification {
+  NSWindow* window = [notification object];
+  NSSize size = [[window contentView] frame].size;
+  gfx::Rect new_bounds(gfx::Point(window.frame.origin), gfx::Size(size));
+  bool prevent_default = false;
+
+  // prevent_default has no effect
+  shell_->NotifyWindowWillMove(new_bounds, &prevent_default);
+}
+
 - (void)windowDidMove:(NSNotification*)notification {
   [super windowDidMove:notification];
   // TODO(zcbenz): Remove the alias after figuring out a proper