You should be able to use the <base>
html tag in the VF page markup to target the links within the iframe to open in the top-most window.
This works with other types of items rendered within Visualforce Home Page Components and should, in theory, work with the charts as well.
<apex:page >
<!-- all links in this VF page will target the top-most window element -->
<base target="_top" />
<analytics:reportChart reportId="XXX" size="tiny" cacheResults="false"></analytics:reportChart>
</apex:page>
Similarly, an example that uses the enhancedList
tag in a VF page embedded within a Home Page Component (iframe).
<apex:page showHeader="true" sidebar="false">
<base target="_top" />
<apex:enhancedList type="Activity" height="300" rowsPerPage="10" />
</apex:page>