The test verifies CSS.getMatchedStylesForNode when used concurrently with the CSSOM modifications for external stylesheets.

Running test: testModifyRule
--------------
Original rule:
*#modifyRule* {    regular
    box-sizing: border-box; @[1:4-1:27]
    box-sizing: border-box; @[undefined-undefined]
}
*#modifyRule* {    regular
    height: 100%; @[5:4-5:17]
    height: 100%; @[undefined-undefined]
}
*#modifyRule* {    regular
    width: 100%; @[9:4-9:16]
    width: 100%; @[undefined-undefined]
}
--------------
Modified rule 1:
*#modifyRule* {    regular    readonly
    box-sizing: border-box; @[undefined-undefined]
    color: red; @[undefined-undefined]
}
*#modifyRule* {    regular
    height: 100%; @[5:4-5:17]
    height: 100%; @[undefined-undefined]
}
*#modifyRule* {    regular
    width: 100%; @[9:4-9:16]
    width: 100%; @[undefined-undefined]
}
---------------
Modified rule 3:
*#modifyRule* {    regular    readonly
    box-sizing: border-box; @[undefined-undefined]
    color: red; @[undefined-undefined]
}
*#modifyRule* {    regular
    height: 100%; @[5:4-5:17]
    height: 100%; @[undefined-undefined]
}
*#modifyRule* {    regular    readonly
    width: 100%; @[undefined-undefined]
    color: blue; @[undefined-undefined]
}
---------------
Modified rule 2:
*#modifyRule* {    regular    readonly
    box-sizing: border-box; @[undefined-undefined]
    color: red; @[undefined-undefined]
}
*#modifyRule* {    regular    readonly
    height: 100%; @[undefined-undefined]
    color: green; @[undefined-undefined]
}
*#modifyRule* {    regular    readonly
    width: 100%; @[undefined-undefined]
    color: blue; @[undefined-undefined]
}
---------------
Restored rule 2:
*#modifyRule* {    regular    readonly
    box-sizing: border-box; @[undefined-undefined]
    color: red; @[undefined-undefined]
}
*#modifyRule* {    regular
    height: 100%; @[5:4-5:17]
    height: 100%; @[undefined-undefined]
}
*#modifyRule* {    regular    readonly
    width: 100%; @[undefined-undefined]
    color: blue; @[undefined-undefined]
}
-----------------
Restored rule 1,3:
*#modifyRule* {    regular
    box-sizing: border-box; @[1:4-1:27]
    box-sizing: border-box; @[undefined-undefined]
}
*#modifyRule* {    regular
    height: 100%; @[5:4-5:17]
    height: 100%; @[undefined-undefined]
}
*#modifyRule* {    regular
    width: 100%; @[9:4-9:16]
    width: 100%; @[undefined-undefined]
}

Running test: testInsertFirstRule
Original rule:
*#insertRule* {    regular
    box-sizing: border-box; @[1:4-1:27]
    box-sizing: border-box; @[undefined-undefined]
}
*#insertRule* {    regular
    width: 100%; @[5:4-5:16]
    width: 100%; @[undefined-undefined]
}
--------------
After inserted rule:
*#insertRule* {    regular    readonly
    color: red; @[undefined-undefined]
}
*#insertRule* {    regular
    box-sizing: border-box; @[1:4-1:27]
    box-sizing: border-box; @[undefined-undefined]
}
*#insertRule* {    regular
    width: 100%; @[5:4-5:16]
    width: 100%; @[undefined-undefined]
}
--------------
Restored rule:
*#insertRule* {    regular
    box-sizing: border-box; @[1:4-1:27]
    box-sizing: border-box; @[undefined-undefined]
}
*#insertRule* {    regular
    width: 100%; @[5:4-5:16]
    width: 100%; @[undefined-undefined]
}

Running test: testInsertMiddleRule
Original rule:
*#insertRule* {    regular
    box-sizing: border-box; @[1:4-1:27]
    box-sizing: border-box; @[undefined-undefined]
}
*#insertRule* {    regular
    width: 100%; @[5:4-5:16]
    width: 100%; @[undefined-undefined]
}
--------------
After inserted rule:
*#insertRule* {    regular
    box-sizing: border-box; @[1:4-1:27]
    box-sizing: border-box; @[undefined-undefined]
}
*#insertRule* {    regular    readonly
    color: red; @[undefined-undefined]
}
*#insertRule* {    regular
    width: 100%; @[5:4-5:16]
    width: 100%; @[undefined-undefined]
}
--------------
Restored rule:
*#insertRule* {    regular
    box-sizing: border-box; @[1:4-1:27]
    box-sizing: border-box; @[undefined-undefined]
}
*#insertRule* {    regular
    width: 100%; @[5:4-5:16]
    width: 100%; @[undefined-undefined]
}

Running test: testInsertLastRule
Original rule:
*#insertRule* {    regular
    box-sizing: border-box; @[1:4-1:27]
    box-sizing: border-box; @[undefined-undefined]
}
*#insertRule* {    regular
    width: 100%; @[5:4-5:16]
    width: 100%; @[undefined-undefined]
}
--------------
After inserted rule:
*#insertRule* {    regular
    box-sizing: border-box; @[1:4-1:27]
    box-sizing: border-box; @[undefined-undefined]
}
*#insertRule* {    regular
    width: 100%; @[5:4-5:16]
    width: 100%; @[undefined-undefined]
}
*#insertRule* {    regular    readonly
    color: red; @[undefined-undefined]
}
--------------
Restored rule:
*#insertRule* {    regular
    box-sizing: border-box; @[1:4-1:27]
    box-sizing: border-box; @[undefined-undefined]
}
*#insertRule* {    regular
    width: 100%; @[5:4-5:16]
    width: 100%; @[undefined-undefined]
}

Running test: testRemoveRule
Original rule:
*#removeRule* {    regular
    box-sizing: border-box; @[1:4-1:27]
    box-sizing: border-box; @[undefined-undefined]
}
*#removeRule* {    regular
    width: 100%; @[5:4-5:16]
    width: 100%; @[undefined-undefined]
}
-------------------
After remove rule 1:
*#removeRule* {    regular
    width: 100%; @[5:4-5:16]
    width: 100%; @[undefined-undefined]
}
-------------------
After remove rule 2:

Running test: testMatchingPrefix
Original rule:
*#matchingPrefix* {    regular
    color: red; @[1:4-1:15]
    color: red; @[undefined-undefined]
}
*#matchingPrefix* {    regular
    color: blue; @[5:4-5:16]
    color: blue; @[undefined-undefined]
}
*#matchingPrefix* {    regular
    color: green; @[9:4-9:17]
    color: green; @[undefined-undefined]
}
--------------
Modified rule 3:
*#matchingPrefix* {    regular
    color: red; @[1:4-1:15]
    color: red; @[undefined-undefined]
}
*#matchingPrefix* {    regular
    color: blue; @[5:4-5:16]
    color: blue; @[undefined-undefined]
}
*#matchingPrefix* {    regular    readonly
    color: purple; @[undefined-undefined]
}

Running test: testMatchingSuffix
Original rule:
*#matchingSuffix* {    regular
    color: red; @[1:4-1:15]
    color: red; @[undefined-undefined]
}
*#matchingSuffix* {    regular
    color: blue; @[5:4-5:16]
    color: blue; @[undefined-undefined]
}
*#matchingSuffix* {    regular
    color: green; @[9:4-9:17]
    color: green; @[undefined-undefined]
}
--------------
Modified rule 0:
*#matchingSuffix* {    regular    readonly
    color: purple; @[undefined-undefined]
}
*#matchingSuffix* {    regular
    color: blue; @[5:4-5:16]
    color: blue; @[undefined-undefined]
}
*#matchingSuffix* {    regular
    color: green; @[9:4-9:17]
    color: green; @[undefined-undefined]
}