Downloading PDF content in iframe with source url not having .pdf extentions

I am trying to download pdf file that is generated dynamically using python.

Inspect element iframe looks something like this.

name="detail" src="/service/displayMailStream.a?importSummaryId=513221314664&lang=en&OWASP_CSRFTOKEN=ZjI2ZTU3MTYt313123MzVhNS0xMWViLWIwNjktMDA1MDU2ODYzZDU0#navpanes=0&toolbar=1&view=fitH" frameborder="0"

The Actual URL when opening the link which has PDF content is:

The pdf viewer plugin has the download button which can be clicked and pdf will be downloaded.

However is there a way for chrome to download the pdf immediately after the url is opened (Chrome PDF download automatically is set to Yes but this requires the download button to be clicked)

I could try to click the download button via selenium but the button cannot be accessed by ID.
Because the button is under #Document == $0.

Any one have this working ?

Source: Ask Javascript Questions