How to browse Android source code at a particular version?

I know that android source code is kept here: https://android.googlesource.com/, but I can't see any way to browse an old version of the code.

How would I view, say, dalvik/libcore/conc开发者_如何学Pythonurrent/src/main/java/java/util/concurrent/LinkedBlockingQueue.java in Froyo?

Try clicking on the platform/dalvik repository. Then scroll down to either one of the tags, or else the froyo-release branch (under Branches). Then just keep following the tree links until you get to the right directory. Then click on the the file you're interested in.

E.g. https://android.googlesource.com/platform/dalvik/+/froyo-release/libcore/concurrent/src/main/java/java/util/concurrent/LinkedBlockingQueue.java

You can browse any version online on AndroidxRef.com and following is your file that you are looking for -- http://androidxref.com/2.2.3/xref/prebuilt/sdk/4/android.jar

This week Google unveiled their official Code Search with Cross References for the Android Open Source Project.
To see Froyo's LinkedBlockingQueue source code you can navigate to this page.