CachedScript and CachedCSSStyleSheet both derive from CachedResource. CachedResource contains a StringBuffer m_data.
Internally, when data is assigned to the CachedScript and CachedCSSStyleSheet, they decode the m_data buffer, and store the result into a private string (m_script and m_sheet, respectively).
Thus, each of these objects has two in-memory copies of the cached object. The m_data is actually not needed and can be removed. The only thing which uses it is the InspectorController; and that usage can be removed with a small amount of work.
For www.cnn.com, this led to a 600KB footprint reduction.
For www.yahoo.com, this led to a ~2MB footprint reduction.
I will post a patch when it's ready.
*** Bug 18956 has been marked as a duplicate of this bug. ***
Is this still an issue?