[One (M7) Themes and Apps] agentdr8:
It's defined as a drawable resource alias in framework-res.apk.

<?xml version="1.0" encoding="utf-8"?>
<resources>
<item type="drawable" name="alert_dark_frame">@drawable/popup_full_dark</item>
<item type="drawable" name="alert_light_frame">@drawable/popup_full_bright</item>
<item type="drawable" name="dialog_frame">@drawable/panel_background</item>
<item type="drawable" name="editbox_dropdown_dark_frame">@drawable/editbox_dropdown_background_dark</item>
<item type="drawable" name="editbox_dropdown_light_frame">@drawable/editbox_dropdown_background</item>
<item type="drawable" name="menu_frame">@drawable/menu_background</item>
<item type="drawable" name="menu_full_frame">@drawable/menu_background_fill_parent_width</item>
<item type="drawable" name="stat_notify_sync_noanim">@drawable/stat_notify_sync_anim0</item>
[B] <item type="drawable" name="stat_sys_download_done">@drawable/stat_sys_download_done_static</item>[/B]
<item type="drawable" name="stat_sys_upload_done">@drawable/stat_sys_upload_anim0</item>
<item type="drawable" name="screen_background_dark">#ff000000</item>
<item type="drawable" name="screen_background_light">#ffffffff</item>
<item type="drawable" name="screen_background_dark_transparent">#80000000</item>
<item type="drawable" name="screen_background_light_transparent">#80ffffff</item>
<item type="drawable" name="dialog_holo_dark_frame">@drawable/dialog_full_holo_dark</item>
<item type="drawable" name="dialog_holo_light_frame">@drawable/dialog_full_holo_light</item>
<item type="drawable" name="status_bar_closed_default_background">#ff000000</item>
<item type="drawable" name="status_bar_opened_default_background">#ff000000</item>
<item type="drawable" name="notification_item_background_color">#ff111111</item>
<item type="drawable" name="notification_item_background_color_pressed">#ff454545</item>
<item type="drawable" name="search_bar_default_color">#ff000000</item>
<item type="drawable" name="safe_mode_background">#60000000</item>
<item type="drawable" name="input_method_fullscreen_background">#fff9f9f9</item>
<item type="drawable" name="input_method_fullscreen_background_holo">@drawable/screen_background_holo_dark</item>
<item type="drawable" name="selected_day_background">#ff0092f4</item>
<item type="drawable" name="screen_background_holo_light">#fff3f3f3</item>
<item type="drawable" name="screen_background_holo_dark">#ff000000</item>
<item type="drawable" name="notification_template_icon_bg">#ff2c2e2f</item>
<item type="drawable" name="notification_template_icon_low_bg">#ff2c2e2f</item>
</resources>

Instead of using the gui, I usually just adb shell into my phone and tail the error.log directly. Makes finding issues easier.

The scaler applies to all images within the iconpack unless the filename or folder contains the following words:

- anchor

- select

- apps

- framework

- settings

This is because the icon sizes for things like text select handles are a different scale than the statusbar. App-specific replacements aren't always the notification icons, so they get excluded as well. I could probably remove the settings one, as that just applies to the usb icon. I can't recall why I had it in there.