Migrating Wiki/Issues is a bit more involved and not covered here. Migrating downloads has to be done by re-uploading to BitBucket (but at least BitBucket supports binary downloads).
You will need to have a working TortoiseGit install:
- install Git for Windows 
- install TortoiseGit  (which is on Google Code, but probably not for longà
You will next need to create and register an SSH key with BitBucket , PuTTy is installed with TortoiseGit, you can find it in the TortoiseGit bin folder.
SVN to local GIT
First step is to get the SVN to a local repository, copy your SVN address from the Google Code “Source” page
The in the Windows Explorer, right click in your root folder of choice, and click “Git Clone..”, adjust the parameters
Hit ok, and wait for the local copy to be created.
Local GIT to BitBucket
Create your repository in BitBucket
then copy the git url, it can be found directly in the “…” menu to the left under the “Clone” action
Go back to the Windows explorer, right click the directory you just created during the clone, and choose Tortoise Git, Settings, then navigate to Git, Remote
Hit “Add New”, paste in the URL field and remove what’s before ‘[email protected]’, it should look like the above.
You will be asked to fetch from the repository, do it. There is nothing in it, but git does not know that yet, so it needs to fetch at least once.
If you have an SSH key registered with BitBucket, select it in the “Putty Key” field.
Now in the Windows Explorer, right click your directory, select Tortoise Git, Push… and everything should end up on BitBucket.