Propagate User App Model ID to Tray Icon

This PR prevents dozens of items showing up in the notification area
preferences when using Squirrel for Windows, by ensuring that
notification tray items are tied to the User App Model ID.

atom/browser/ui/win/notify_icon.cc

@@ -4,7 +4,10 @@
 
 #include "atom/browser/ui/win/notify_icon.h"
 
+#include <shobjidl.h>
+
 #include "atom/browser/ui/win/notify_icon_host.h"
+#include "base/md5.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/win/windows_version.h"
@@ -26,6 +29,18 @@ NotifyIcon::NotifyIcon(NotifyIconHost* host,
       window_(window),
       message_id_(message),
       menu_model_(NULL) {
+        
+  // NB: If we have an App Model ID, we should propagate that to the tray. 
+  // Doing this prevents duplicate items from showing up in the notification
+  // preferences (i.e. "Always Show / Show notifications only / etc")
+  PWSTR explicit_app_id;
+  
+  if (SUCCEEDED(GetCurrentProcessExplicitAppUserModelID(&explicit_app_id))) {
+    // GUIDs and MD5 hashes are the same length. So convenient!
+    MD5Sum(explicit_app_id, sizeof(wchar_t) * wcslen(explicit_app_id), (MD5Digest*)&tray_app_id_hash_);
+    CoTaskMemFree(explicit_app_id);
+  }
+        
   NOTIFYICONDATA icon_data;
   InitIconData(&icon_data);
   icon_data.uFlags = NIF_MESSAGE;
@@ -161,6 +176,7 @@ void NotifyIcon::InitIconData(NOTIFYICONDATA* icon_data) {
   icon_data->cbSize = sizeof(NOTIFYICONDATA);
   icon_data->hWnd = window_;
   icon_data->uID = icon_id_;
+  memcpy(icon_data->guidItem, tray_app_id_hash_, sizeof(GUID));
 }
 
 }  // namespace atom

atom/browser/ui/win/notify_icon.h

@@ -75,6 +75,9 @@ class NotifyIcon : public TrayIcon {
 
   // The context menu.
   ui::SimpleMenuModel* menu_model_;
+  
+  // A hash of the app model ID
+  GUID tray_app_id_hash_;
 
   DISALLOW_COPY_AND_ASSIGN(NotifyIcon);
 };