Revert of Early preconnection for intent-based startups on Android. (patchset #15...

Revert of Early preconnection for intent-based startups on Android. (patchset #15 id:280001 of https://codereview.chromium.org/924493002/)

Reason for revert:
broke downstream tests

Original issue's description:
> Early preconnection for intent-based startups on Android.
>
> When Chromium starts with an intent, there is a location to navigate to,
> from the intent. However a lot of initialization defers the first
> network activity by more than 1s on fast devices.
>
> A previous CL (https://codereview.chromium.org/909893003/) has added an
> early DNS request to the destination, and this one adds an early
> preconnection to it. The preconnection is possible as soon as the
> network stack is ready, but currently happens after Tab.loadUrl(),
> several 100s of ms later. This patch moves the preconnection earlier.
>
> However, if the early DNS request is still in flight, then the
> preconnection will itself issue a new DNS request, negating the gains
> from the early first one. Assuming that DNS requests come back in order,
> it is then better to delay the preconnection until the DNS answer has
> been obtained.
>
> Note: the associated bug contains a link to a document explaining the
> motivation, testing methodology and experimental results of this change.
>
> BUG=458216
>
> Committed: https://crrev.com/101b4cd231701928089bce1defeb8b5b0cd95659
> Cr-Commit-Position: refs/heads/master@{#319939}

TBR=pasko@chromium.org,nyquist@chromium.org,lizeb@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=458216

Review URL: https://codereview.chromium.org/994213002

Cr-Commit-Position: refs/heads/master@{#319997}