Return ActiveSheetsChanged when rulesets change in common prefix.

Return ActiveSheetsChanged when rulesets change in common prefix.

When comparing old and new active sheets, we only append the added
sheets to the ScopedStyleResolver if the old sheet vector is a prefix
of the new sheets. However, that's not correct if any of the RuleSets
in the common prefix changed due to media query changes or cssom
modifications of a stylesheet.

I can confirm that this fixes 681472. The other two issues in the BUG
field look like duplicates, but I've not been able to reproduce them.

R=meade@chromium.org,sashab@chromium.org
BUG=681472, 677371, 681882
Review-Url: https://codereview.chromium.org/2650743002
Cr-Commit-Position: refs/heads/master@{#446008}
(cherry picked from commit 67cfc67e3b62993bb0df9395559e1d1a76d26213)

Review-Url: https://codereview.chromium.org/2655283002 .
Cr-Commit-Position: refs/branch-heads/2987@{#102}
Cr-Branched-From: ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed: https://chromium.googlesource.com/chromium/src/+/4833c6af7aed66bb1fc500f45f43d6476b890b86

[rune, 2017-01-26 14:00:18]

Description was changed from

==========
Return ActiveSheetsChanged when rulesets change in common prefix.

When comparing old and new active sheets, we only append the added
sheets to the ScopedStyleResolver if the old sheet vector is a prefix
of the new sheets. However, that's not correct if any of the RuleSets
in the common prefix changed due to media query changes or cssom
modifications of a stylesheet.

I can confirm that this fixes 681472. The other two issues in the BUG
field look like duplicates, but I've not been able to reproduce them.

R=meade@chromium.org,sashab@chromium.org
BUG=681472,677371,681882

Review-Url: https://codereview.chromium.org/2650743002
Cr-Commit-Position: refs/heads/master@{#446008}
(cherry picked from commit 67cfc67e3b62993bb0df9395559e1d1a76d26213)
==========

to

==========
Return ActiveSheetsChanged when rulesets change in common prefix.

When comparing old and new active sheets, we only append the added
sheets to the ScopedStyleResolver if the old sheet vector is a prefix
of the new sheets. However, that's not correct if any of the RuleSets
in the common prefix changed due to media query changes or cssom
modifications of a stylesheet.

I can confirm that this fixes 681472. The other two issues in the BUG
field look like duplicates, but I've not been able to reproduce them.

R=meade@chromium.org,sashab@chromium.org
BUG=681472,677371,681882

Review-Url: https://codereview.chromium.org/2650743002
Cr-Commit-Position: refs/heads/master@{#446008}
(cherry picked from commit 67cfc67e3b62993bb0df9395559e1d1a76d26213)

Review-Url: https://codereview.chromium.org/2655283002 .
Cr-Commit-Position: refs/branch-heads/2987@{#102}
Cr-Branched-From:
ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed:
https://chromium.googlesource.com/chromium/src/+/4833c6af7aed66bb1fc500f45f43...
==========

[rune, 2017-01-26 14:00:20]

Committed patchset #1 (id:1) manually as
4833c6af7aed66bb1fc500f45f43d6476b890b86.