DevTools: "JS sampling" checkbox should not affect recorded profile

The checkbos now affects only the next recorded profile. Presentation of the existing one does not change.

BUG=426149

Review URL: https://codereview.chromium.org/695843002

git-svn-id: svn://svn.chromium.org/blink/trunk@184734 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: disable zoom on empty Timeline

BUG=426764

Review URL: https://codereview.chromium.org/696683002

git-svn-id: svn://svn.chromium.org/blink/trunk@184737 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: don't allow to zoom flame chart in more than 10us window

Zoom in will stop on flame chart once the width of the visible time range is less than 10us. This helps us avoid long overlapping lavels on the overview scale and fixes broken zoom controls after zooming in too much.

BUG=426764

Review URL: https://codereview.chromium.org/683243007

git-svn-id: svn://svn.chromium.org/blink/trunk@184740 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: [SSP] simplify sidebar panes update

The patch removes woeful "needsUpdate" flags that were set by
ElementsPanel on its sidebar panes.

Now, "update" methods of all sidebars in ElementsPanel postpone work to
update rendering until it becomes visible.

BUG=427396
R=apavlov, pfeldman

Review URL: https://codereview.chromium.org/688613003

git-svn-id: svn://svn.chromium.org/blink/trunk@184744 bbb929c8-8fbe-4397-9dbb-9b2b20218538