GitLab

Merges settings-basic-page and settings-advanced-page by into one element.

This simplifies a lot of behavior (we no longer have two MainPageBehavior
instances trying to scroll #mainContainter at the same time) which fixes some
bugs for free.

Functionality in settings-main that was specific to the settings pages has
been moved into settings-basic page, simplifying settings-main. Unfortunately,
settings-main still shares an annoying amount with setting-basic-page, namely
inSearchMode and advancedToggleExpanded.

The main bug this fixes is issue 662004: tapping a Basic page section from an
Advanced page sub-page (or vice versa) would fail to scroll to the new section.

Minor bugs that this fixes:
* after opening a subpage, tapping a section in the nav menu closed the subpage
    but only jumped to the new section after an awkward delay
* after loading a subpage URL, tapping the back icon button caused the page to
    jump to the top, then back down
* navigating from a Basic subpage to an Advanced subpage, or vice versa, would
    have hidden one of the main pages while transitioning

Note: settings-basic-page should be renamed now that "basic" is meaningless, but
unfortunately every conceivable alternative name is already taken, except for
settings-settings-page which is horrible for reasons too numerous to mention.

BUG=662004
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2518233004
Cr-Commit-Position: refs/heads/master@{#438738}