Multimedia macro should determine media dimensions from file

When embedding using the multimedia macro (for example, a .mov), with no height/width explicitly specified, the Confluence page will display a fixed-size viewport regardless of the actual dimensions of the media.

Example wiki markup:

{multimedia:name=example.mov}

Moreover, if the media dimensions are larger than the viewport, the macro will not scale the embedded media down to fit the view. This causes a few problems, because not only does the media get cut off, the playback bar can also be cut out, leaving it difficult/impossible for the user to control playback. (Tested this with a 640x480 sample .mov file from http://support.apple.com/kb/HT1425)

The documentation states that "If not specified, the browser will determine the width/height based on the file type", but doesn't seem clear what this actually means. If this means that, regardless of actual file dimensions, Confluence will display certain formats in certain fixed-sizes, we should clarify this in the documentation.

Right now the user has to explicitly declare height/width parameters larger than the dimensions of the media, but this does not seem ideal. Possible solutions are to either pick up the dimensions and automatically resize the viewport accordingly, or to scale the media to fit in the fixed-sized viewport. If the latter is intended, then this ticket would be a duplicate of https://jira.atlassian.com/browse/CONF-22240