fix: non-client mouse events on WCO-enabled windows

patches/chromium/.patches

@@ -113,3 +113,4 @@ fix_crash_when_saving_edited_pdf_files.patch
 port_autofill_colors_to_the_color_pipeline.patch
 build_disable_partition_alloc_on_mac.patch
 build_disable_thin_lto_on_mac.patch
+fix_non-client_mouse_tracking_and_message_bubbling_on_windows.patch

patches/chromium/fix_non-client_mouse_tracking_and_message_bubbling_on_windows.patch

@@ -0,0 +1,61 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: clavin <cwatford@slack-corp.com>
+Date: Fri, 11 Feb 2022 15:05:42 -0700
+Subject: fix: non-client mouse tracking and message bubbling on windows
+
+It is not known why, but for some reason calling |DefWindowProc| on the parent
+window handle causes a WM_NCMOUSELEAVE (non-client mouse exit) message to be
+sent to the parent window, even though |TrackMouseEvent| is never called on it.
+
+This patch also adds some boilerplate for properly tracking non-client mouse
+messages in the legacy window handle layer.
+
+These conditions are regularly hit with WCO-enabled windows on Windows.
+
+diff --git a/content/browser/renderer_host/legacy_render_widget_host_win.cc b/content/browser/renderer_host/legacy_render_widget_host_win.cc
+index 4a894ef70eeb1d8489049aef552c9bae4f24ae62..f5049d730a850f2947023f976b25fb772e42107a 100644
+--- a/content/browser/renderer_host/legacy_render_widget_host_win.cc
++++ b/content/browser/renderer_host/legacy_render_widget_host_win.cc
+@@ -288,12 +288,12 @@ LRESULT LegacyRenderWidgetHostHWND::OnMouseRange(UINT message,
+                                                  WPARAM w_param,
+                                                  LPARAM l_param,
+                                                  BOOL& handled) {
+-  if (message == WM_MOUSEMOVE) {
++  if (message == WM_MOUSEMOVE || message == WM_NCMOUSEMOVE) {
+     if (!mouse_tracking_enabled_) {
+       mouse_tracking_enabled_ = true;
+       TRACKMOUSEEVENT tme;
+       tme.cbSize = sizeof(tme);
+-      tme.dwFlags = TME_LEAVE;
++      tme.dwFlags = message == WM_NCMOUSEMOVE ? TME_NONCLIENT | TME_LEAVE : TME_LEAVE;
+       tme.hwndTrack = hwnd();
+       tme.dwHoverTime = 0;
+       TrackMouseEvent(&tme);
+@@ -319,12 +319,11 @@ LRESULT LegacyRenderWidgetHostHWND::OnMouseRange(UINT message,
+         message, w_param, l_param, &msg_handled);
+     handled = msg_handled;
+     // If the parent did not handle non client mouse messages, we call
+-    // DefWindowProc on the message with the parent window handle. This
+-    // ensures that WM_SYSCOMMAND is generated for the parent and we are
+-    // out of the picture.
++    // DefWindowProc on the message. This ensures that WM_SYSCOMMAND is
++    // generated.
+     if (!handled &&
+          (message >= WM_NCMOUSEMOVE && message <= WM_NCXBUTTONDBLCLK)) {
+-      ret = ::DefWindowProc(GetParent(), message, w_param, l_param);
++      ret = ::DefWindowProc(hwnd(), message, w_param, l_param);
+       handled = TRUE;
+     }
+   }
+diff --git a/content/browser/renderer_host/legacy_render_widget_host_win.h b/content/browser/renderer_host/legacy_render_widget_host_win.h
+index 79dffd981f4d461f30bd3796cfba1457eda3a89d..ae378ce95f90989fd0e74c38b57f5f7dc0a1ee29 100644
+--- a/content/browser/renderer_host/legacy_render_widget_host_win.h
++++ b/content/browser/renderer_host/legacy_render_widget_host_win.h
+@@ -105,6 +105,7 @@ class CONTENT_EXPORT LegacyRenderWidgetHostHWND
+     MESSAGE_HANDLER_EX(WM_NCHITTEST, OnNCHitTest)
+     MESSAGE_RANGE_HANDLER(WM_NCMOUSEMOVE, WM_NCXBUTTONDBLCLK,
+                           OnMouseRange)
++    MESSAGE_HANDLER_EX(WM_NCMOUSELEAVE, OnMouseLeave)
+     MESSAGE_HANDLER_EX(WM_NCCALCSIZE, OnNCCalcSize)
+     MESSAGE_HANDLER_EX(WM_SIZE, OnSize)
+     MESSAGE_HANDLER_EX(WM_DESTROY, OnDestroy)

shell/browser/ui/win/electron_desktop_window_tree_host_win.cc

@@ -99,21 +99,4 @@ bool ElectronDesktopWindowTreeHostWin::GetClientAreaInsets(
   return false;
 }
 
-bool ElectronDesktopWindowTreeHostWin::HandleMouseEvent(ui::MouseEvent* event) {
-  // Call the default implementation of this method to get the event to its
-  // proper handler.
-  bool handled = views::DesktopWindowTreeHostWin::HandleMouseEvent(event);
-
-  // On WCO-enabled windows, we need to mark non-client mouse moved events as
-  // handled so they don't incorrectly propogate back to the OS.
-  if (native_window_view_->IsWindowControlsOverlayEnabled() &&
-      event->type() == ui::ET_MOUSE_MOVED &&
-      (event->flags() & ui::EF_IS_NON_CLIENT) != 0) {
-    event->SetHandled();
-    handled = true;
-  }
-
-  return handled;
-}
-
 }  // namespace electron

shell/browser/ui/win/electron_desktop_window_tree_host_win.h

@@ -36,7 +36,6 @@ class ElectronDesktopWindowTreeHostWin
   bool GetDwmFrameInsetsInPixels(gfx::Insets* insets) const override;
   bool GetClientAreaInsets(gfx::Insets* insets,
                            HMONITOR monitor) const override;
-  bool HandleMouseEvent(ui::MouseEvent* event) override;
 
  private:
   NativeWindowViews* native_window_view_;  // weak ref