[DevTools] Simplify getting back to default network order.

[DevTools] Simplify getting back to default network order.

Column header "Timeline" in NetworkPanel is actually a combo-box. This is a very confusing UI.
In this patch combobox and all related code is eliminated.

BUG=462189
Original patch by eustas@chromium.org. https://codereview.chromium.org/1048823002/

[dgozman, 2015-04-30 11:20:01]

dgozman@chromium.org changed reviewers:
+ pfeldman@chromium.org

[dgozman, 2015-04-30 11:20:02]

Take a look please.

[dgozman, 2015-05-13 01:17:08]

dgozman@chromium.org changed reviewers:
+ paulirish@chromium.org

[dgozman, 2015-05-13 01:17:09]

Ping. +Paul, do you think that removing this functionality is a good idea?

[pfeldman, 2015-05-15 23:40:10]

On 2015/05/13 01:17:09, dgozman_ooo wrote:
> Ping. +Paul, do you think that removing this functionality is a good idea?

not lgtm.

We still want to sort by duration and that should change the calculator.

[dgozman, 2015-05-16 01:37:04]

On 2015/05/15 23:40:10, pfeldman_slow wrote:
> On 2015/05/13 01:17:09, dgozman_ooo wrote:
> > Ping. +Paul, do you think that removing this functionality is a good idea?
> 
> not lgtm.
> 
> We still want to sort by duration and that should change the calculator.

Please mention your objections in the bug so we can resolve it.

[pfeldman, 2015-05-16 13:41:23]

I have no problem with the bug, it is just your implementation that is
regressing a bit more than the bug says.

[paulirish, 2015-05-16 23:47:17]

On 2015/05/13 at 01:17:09, dgozman wrote:
> Ping. +Paul, do you think that removing this functionality is a good idea?


I've never liked the combo box that's completely hidden. 
But I've also encountered the bug in https://crbug.com/462189

Since this becomes more about UX let's pick it up the discussion there.