DevTools: follow up to r170181, narrow add new rule button a bit.

BUG=358095

Review URL: https://codereview.chromium.org/245063003

git-svn-id: svn://svn.chromium.org/blink/trunk@172060 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: mark only text-decorated timeline entries as such.

Review URL: https://codereview.chromium.org/245183002

git-svn-id: svn://svn.chromium.org/blink/trunk@172061 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: Make timeline events overview strip more sparse for rare events.

Review URL: https://codereview.chromium.org/245283003

git-svn-id: svn://svn.chromium.org/blink/trunk@172062 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Tentatively enable HTMLImports flag to ensure its ship-ability.

TEST=none
R=dglazkov,esprehn
BUG=240592

Review URL: https://codereview.chromium.org/245443002

git-svn-id: svn://svn.chromium.org/blink/trunk@172063 bbb929c8-8fbe-4397-9dbb-9b2b20218538