diff --git a/dom/plugins/base/nsPluginNativeWindowGtk2.cpp b/dom/plugins/base/nsPluginNativeWindowGtk2.cpp
index 38e13ee..f5f622b 100644
--- a/dom/plugins/base/nsPluginNativeWindowGtk2.cpp
+++ b/dom/plugins/base/nsPluginNativeWindowGtk2.cpp
@@ -16,6 +16,7 @@
 #include <gtk/gtk.h>
 #include <gdk/gdkx.h>
 #include <gdk/gdk.h>
+#include <gdk/gdkkeysyms.h>
 
 #include "gtk2xtbin.h"
 #include "mozilla/X11Util.h"
@@ -157,6 +158,82 @@ nsresult nsPluginNativeWindowGtk2::CallSetWindow(nsRefPtr<nsNPAPIPluginInstance>
   return NS_OK;
 }
 
+// Adapted from patch on https://bugzilla.mozilla.org/show_bug.cgi?id=78414
+gboolean on_key_press(GtkWidget *window, GdkEventKey *pKey, gpointer data) {
+  GtkWidget *parent_widget;
+  gboolean combination_keypress = FALSE;
+  gboolean F1_to_F12 = FALSE;
+  gboolean plugin_text_edit_keys = FALSE;
+
+  /* Should the plugin or Firefox receive the key?
+   * 1. If it's a regular key, the plugin
+   * 2. If it's F1-F12, Firefox
+   * 3. If it's a common modifier key, not in a combination with another key, the plugin
+   * 4. If it's a common modifier key (except shift) in combination with another key, Firefox
+   * 5. If it's ctrl-z, ctrl-x, ctrl-c or ctrl-v, the plugin
+   */
+
+  /* Firefox priority keys:
+   *  F1 to F12
+   */
+  if (pKey->type == GDK_KEY_PRESS) {
+    switch (pKey->keyval)
+    {
+      /* Fallthrough */
+      case GDK_KEY_F1:
+      case GDK_KEY_F2:
+      case GDK_KEY_F3:
+      case GDK_KEY_F4:
+      case GDK_KEY_F5:
+      case GDK_KEY_F6:
+      case GDK_KEY_F7:
+      case GDK_KEY_F8:
+      case GDK_KEY_F9:
+      case GDK_KEY_F10:
+      case GDK_KEY_F11:
+      case GDK_KEY_F12:
+        /* The keypress is F1-F12 */
+        F1_to_F12 = TRUE;
+        break;
+    }
+  }
+
+  /* This is not a single modifier-key keypress (like Ctrl by itself) */
+  if (pKey->state & (GDK_CONTROL_MASK | GDK_MOD1_MASK)) {
+    /* This is a combination of a modifier and a keypress */
+    combination_keypress = TRUE;
+  }
+
+  /* Flash priority keys:
+   *  Ctrl-Z, Ctrl-X, Ctrl-C, Ctrl-V, Ctrl-A
+   */
+  if (combination_keypress) {
+    switch (pKey->keyval)
+    {
+      /* Fallthrough */
+      case GDK_KEY_z:
+      case GDK_KEY_x:
+      case GDK_KEY_c:
+      case GDK_KEY_v:
+      case GDK_KEY_a:
+        /* Yes, it's one of the plugin text editing keys */
+        plugin_text_edit_keys = TRUE;
+        break;
+    }
+  }
+
+  if (((!F1_to_F12) && (!combination_keypress)) || (plugin_text_edit_keys)) {
+    /* The plugin should receive this keypress */
+    return FALSE;
+  } else {
+    /* Change focus to the parent widget */
+    parent_widget = gtk_widget_get_parent(window);
+    gtk_widget_grab_focus(parent_widget);
+    /* The keypress will be handled by the parent widget (Firefox) */
+    return FALSE;
+  }
+}
+
 nsresult nsPluginNativeWindowGtk2::CreateXEmbedWindow(bool aEnableXtFocus) {
   NS_ASSERTION(!mSocketWidget,"Already created a socket widget!");
   GdkDisplay *display = gdk_display_get_default();
@@ -183,6 +260,9 @@ nsresult nsPluginNativeWindowGtk2::CreateXEmbedWindow(bool aEnableXtFocus) {
   g_signal_connect(mSocketWidget, "destroy",
                    G_CALLBACK(gtk_widget_destroyed), &mSocketWidget);
 
+  g_signal_connect(mSocketWidget, "key-press-event",
+                   G_CALLBACK(on_key_press), NULL);
+
   gpointer user_data = NULL;
   gdk_window_get_user_data(parent_win, &user_data);