There isn't a backdrop. This is the definition
Code:
<Frame name="UIDropDownMenuTemplate" virtual="true">
<Size x="40" y="32"/>
<Layers>
<Layer level="ARTWORK">
<Texture name="$parentLeft" parentKey="Left" file="Interface\Glues\CharacterCreate\CharacterCreate-LabelFrame">
<Size x="25" y="64"/>
<Anchors>
<Anchor point="TOPLEFT" x="0" y="17"/>
</Anchors>
<TexCoords left="0" right="0.1953125" top="0" bottom="1"/>
</Texture>
<Texture name="$parentMiddle" parentKey="Middle" file="Interface\Glues\CharacterCreate\CharacterCreate-LabelFrame">
<Size x="115" y="64"/>
<Anchors>
<Anchor point="LEFT" relativeKey="$parent.Left" relativePoint="RIGHT"/>
</Anchors>
<TexCoords left="0.1953125" right="0.8046875" top="0" bottom="1"/>
</Texture>
<Texture name="$parentRight" parentKey="Right" file="Interface\Glues\CharacterCreate\CharacterCreate-LabelFrame">
<Size x="25" y="64"/>
<Anchors>
<Anchor point="LEFT" relativeKey="$parent.Middle" relativePoint="RIGHT"/>
</Anchors>
<TexCoords left="0.8046875" right="1" top="0" bottom="1"/>
</Texture>
<FontString parentKey="Text" name="$parentText" inherits="GameFontHighlightSmall" wordwrap="false" justifyH="RIGHT">
<Size x="0" y="10"/>
<Anchors>
<Anchor point="RIGHT" relativeKey="$parent.Right" x="-43" y="2"/>
</Anchors>
</FontString>
</Layer>
<Layer level="OVERLAY">
<Texture parentKey="Icon" name="$parentIcon" hidden="true">
<Size x="16" y="16"/>
<Anchors>
<Anchor point="LEFT">
<Offset x="30" y="2"/>
</Anchor>
</Anchors>
</Texture>
</Layer>
</Layers>
<Frames>
<DropDownToggleButton parentKey="Button" name="$parentButton" inherits="UIDropDownMenuButtonScriptTemplate" motionScriptsWhileDisabled="true" >
<Size x="24" y="24"/>
<Anchors>
<Anchor point="TOPRIGHT" relativeKey="$parent.Right" x="-16" y="-18"/>
</Anchors>
<NormalTexture name="$parentNormalTexture" parentKey="NormalTexture" file="Interface\ChatFrame\UI-ChatIcon-ScrollDown-Up">
<Size x="24" y="24"/>
<Anchors>
<Anchor point="RIGHT"/>
</Anchors>
</NormalTexture>
<PushedTexture name="$parentPushedTexture" parentKey="PushedTexture" file="Interface\ChatFrame\UI-ChatIcon-ScrollDown-Down">
<Size x="24" y="24"/>
<Anchors>
<Anchor point="RIGHT"/>
</Anchors>
</PushedTexture>
<DisabledTexture name="$parentDisabledTexture" parentKey="DisabledTexture" file="Interface\ChatFrame\UI-ChatIcon-ScrollDown-Disabled">
<Size x="24" y="24"/>
<Anchors>
<Anchor point="RIGHT"/>
</Anchors>
</DisabledTexture>
<HighlightTexture name="$parentHighlightTexture" parentKey="HighlightTexture" file="Interface\Buttons\UI-Common-MouseHilight" alphaMode="ADD">
<Size x="24" y="24"/>
<Anchors>
<Anchor point="RIGHT"/>
</Anchors>
</HighlightTexture>
</DropDownToggleButton>
</Frames>
<Scripts>
<OnHide>
CloseDropDownMenus();
</OnHide>
</Scripts>
</Frame>