Turning on ssl in magento admin pages requires extra effort.
Magento uses google chart to generate order diagrams making requests to http://chart.apis.google.com/chart.
Up until now google apis can’t use ssl, but now there is a possibility – https://chart.googleapis.com/chart. So all we have to do is to overwrite Mage_Adminhtml_Block_Dashboard_Graph class, which is responsible for charts generation.
Touching core files is a very bad practice, so we copy some files: