DevTools: NetworkPanel: make it easier to click popover content.
DevTools: NetworkPanel: make it easier to click popover content.

BUG=426013

Review URL: https://codereview.chromium.org/687513003

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@184522 bbb929c8-8fbe-4397-9dbb-9b2b20218538

primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs