Omnibox: Don't Trim Trailing Space in Keyword Mode Searches

BUG=313145

Review URL: https://codereview.chromium.org/45733014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232197 0039d316-1c4b-4281-b951-d872f2087c98
Add better documentation for declarativeContent.

I reorganized the declarative-event common HTML so it's more clear that 3
methods are available.

I moved the CSS condition docs into their own section and elaborated on both the
meaning of a compound selector and the display:none restriction.  It's
unfortunate that this isn't just in the PageStateMatcher.css description, but
that has to live on a single line in the json which makes it really hard to
edit.

BUG=172011
NOTRY=true

Review URL: https://codereview.chromium.org/46533002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232198 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232198