DevTools: [Network] Refactorings.
DevTools: [Network] Refactorings.

Prefactorings before adding more columns.

1) Remove row-specific code from status cell rendering.
2) Added _refreshMedhodCell, to make rendering uniform.
3) Make _appendSubtitle static
4) Construst timline cell like other calls.
5) Fix type warning.
6) Added @override JSDoc.

BUG=

Review URL: https://codereview.chromium.org/14264006

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@148814 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