This will also change the expectation format slightly. They are:
* Beginning of test expectations defined all the tags can be used for expressing test condition. Tags are grouped together with brackets,  e.g:

# tags: [
#   Mac Mac10.1 Mac10.2
#   Win Win8
# ]
# tags: [ Release Debug ]

* Tags within a same group are mutually exclusive, means they can't exist together in a expectation line (e.g: a test platform can't be both "Win" & "Mac".
* Specifying many tags in one expectation mean AND. For example:

crbug.com/626703 [ Linux Release ] external/wpt/css/css-text/letter-spacing/letter-spacing-control-chars-001.html [ Failure ]

means external/wpt/css/css-text/letter-spacing/letter-spacing-control-chars-001.html is expected to fail on Linux platform and release build. 


More details can be found in bit.ly/chromium-test-list-format