I've reverted the likely culprit in https://codereview.chromium.org/2452313002/, assigning to pasko@.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f69bf24f0861768f03628206668ddb84f55dc8d4

commit f69bf24f0861768f03628206668ddb84f55dc8d4
Author: foolip <foolip@chromium.org>
Date: Thu Oct 27 09:08:20 2016

Revert of [NoStatePrefetch] Kill renderer after preload scanning (patchset #12 id:240001 of https://codereview.chromium.org/2411863002/ )

Reason for revert:
"NoStatePrefetchBrowserTest.OpenTaskManagerBeforePrefetch" became flaky
shortly after this landed.

BUG= 659697 

Original issue's description:
> [NoStatePrefetch] Kill renderer after preload scanning
>
> The design doc is linked in the first bug. Main goal: remove Prerender.
>
> Currently NoState Prefetch uses the same logic to manage renderers as the
> PrerenderManager. Prefetch code is still living in PrerenderManager, separating
> the code from there is planned after we finalize on how much of the
> functionality of PrerenderManager is needed.
>
> This is the first tweak in the renderer lifetime: the renderer asks to be killed
> as soon as the main resource is fully preload-scanned and all possible
> subresources are requested, special Prerendering FinalStatus is recorded to allow:
> * testing
> * provide a hint that a new prefetch can be started soon
>
> Browsertest changes:
>
> * TestPrerender now keeps FinalStatus for longer, to be able to verify that it
>   is correct even after the TestPrerenderContents is destroyed.
>
> * Prefetch browsertests wait only for creation of PrerenderContents, Prerender
>   tests have more waiting for page loads on top of that
>
> * PrerenderTestUrlImpl is removed to eliminate one hop through protected method
>   in the parent class, which also simplified the prefetch side of the tests: no
>   need to mention how many page loads to wait for
>
> * Disabled two tests that load a non-HTML document, correctly killing the
>   renderer will be done in later changes.
>
> BUG=632361, 649632 
>
> Committed: https://crrev.com/66351bd0a0fc8740749663fe765a301e1a175538
> Cr-Commit-Position: refs/heads/master@{#427678}

TBR=jochen@chromium.org,csharrison@chromium.org,droger@chromium.org,mattcary@chromium.org,mkwst@chromium.org,pasko@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=632361, 649632 

Review-Url: https://codereview.chromium.org/2452313002
Cr-Commit-Position: refs/heads/master@{#427974}

[modify] https://crrev.com/f69bf24f0861768f03628206668ddb84f55dc8d4/chrome/browser/prerender/prerender_browsertest.cc
[modify] https://crrev.com/f69bf24f0861768f03628206668ddb84f55dc8d4/chrome/browser/prerender/prerender_final_status.cc
[modify] https://crrev.com/f69bf24f0861768f03628206668ddb84f55dc8d4/chrome/browser/prerender/prerender_final_status.h
[modify] https://crrev.com/f69bf24f0861768f03628206668ddb84f55dc8d4/chrome/browser/prerender/prerender_manager.cc
[modify] https://crrev.com/f69bf24f0861768f03628206668ddb84f55dc8d4/chrome/browser/prerender/prerender_manager.h
[modify] https://crrev.com/f69bf24f0861768f03628206668ddb84f55dc8d4/chrome/browser/prerender/prerender_message_filter.cc
[modify] https://crrev.com/f69bf24f0861768f03628206668ddb84f55dc8d4/chrome/browser/prerender/prerender_message_filter.h
[modify] https://crrev.com/f69bf24f0861768f03628206668ddb84f55dc8d4/chrome/browser/prerender/prerender_nostate_prefetch_browsertest.cc
[modify] https://crrev.com/f69bf24f0861768f03628206668ddb84f55dc8d4/chrome/browser/prerender/prerender_test_utils.cc
[modify] https://crrev.com/f69bf24f0861768f03628206668ddb84f55dc8d4/chrome/browser/prerender/prerender_test_utils.h
[modify] https://crrev.com/f69bf24f0861768f03628206668ddb84f55dc8d4/chrome/common/prerender_messages.h
[modify] https://crrev.com/f69bf24f0861768f03628206668ddb84f55dc8d4/chrome/renderer/prerender/prerender_dispatcher.cc
[modify] https://crrev.com/f69bf24f0861768f03628206668ddb84f55dc8d4/chrome/renderer/prerender/prerender_dispatcher.h
[modify] https://crrev.com/f69bf24f0861768f03628206668ddb84f55dc8d4/third_party/WebKit/Source/core/dom/Document.cpp
[modify] https://crrev.com/f69bf24f0861768f03628206668ddb84f55dc8d4/third_party/WebKit/Source/web/tests/PrerenderingTest.cpp
[modify] https://crrev.com/f69bf24f0861768f03628206668ddb84f55dc8d4/third_party/WebKit/public/platform/WebPrerenderingSupport.h

No flakes since revert, that was probably the culprit then.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/07afa9f65f71178f9be52e2738303eee3c9fdb0d

commit 07afa9f65f71178f9be52e2738303eee3c9fdb0d
Author: pasko <pasko@chromium.org>
Date: Thu Oct 27 15:01:15 2016

Reland: [NoStatePrefetch] Kill renderer after preload scanning

Remove the inherently flaky test
NoStatePrefetchBrowserTest.OpenTaskManagerBeforePrefetch and revert the
following revert:

> Reason for revert:
> "NoStatePrefetchBrowserTest.OpenTaskManagerBeforePrefetch" became flaky
> shortly after this landed.
>
> BUG= 659697 
> Original issue's description:
> > [NoStatePrefetch] Kill renderer after preload scanning
> >
> > The design doc is linked in the first bug. Main goal: remove Prerender.
> >
> > Currently NoState Prefetch uses the same logic to manage renderers as the
> > PrerenderManager. Prefetch code is still living in PrerenderManager, separating
> > the code from there is planned after we finalize on how much of the
> > functionality of PrerenderManager is needed.
> >
> > This is the first tweak in the renderer lifetime: the renderer asks to be killed
> > as soon as the main resource is fully preload-scanned and all possible
> > subresources are requested, special Prerendering FinalStatus is recorded to allow:
> > * testing
> > * provide a hint that a new prefetch can be started soon
> >
> > Browsertest changes:
> >
> > * TestPrerender now keeps FinalStatus for longer, to be able to verify that it
> >   is correct even after the TestPrerenderContents is destroyed.
> >
> > * Prefetch browsertests wait only for creation of PrerenderContents, Prerender
> >   tests have more waiting for page loads on top of that
> >
> > * PrerenderTestUrlImpl is removed to eliminate one hop through protected method
> >   in the parent class, which also simplified the prefetch side of the tests: no
> >   need to mention how many page loads to wait for
> >
> > * Disabled two tests that load a non-HTML document, correctly killing the
> >   renderer will be done in later changes.
> >
> > BUG=632361,  649632 
> >
> > Committed: https://crrev.com/66351bd0a0fc8740749663fe765a301e1a175538
> > Cr-Commit-Position: refs/heads/master@{#427678}
> Committed: https://crrev.com/f69bf24f0861768f03628206668ddb84f55dc8d4
> Cr-Commit-Position: refs/heads/master@{#427974}

TBR=jochen@chromium.org,csharrison@chromium.org,mattcary@chromium.org,mkwst@chromium.org,pasko@chromium.org
BUG=632361,  649632 

Review-Url: https://codereview.chromium.org/2455653005
Cr-Commit-Position: refs/heads/master@{#428027}

[modify] https://crrev.com/07afa9f65f71178f9be52e2738303eee3c9fdb0d/chrome/browser/prerender/prerender_browsertest.cc
[modify] https://crrev.com/07afa9f65f71178f9be52e2738303eee3c9fdb0d/chrome/browser/prerender/prerender_final_status.cc
[modify] https://crrev.com/07afa9f65f71178f9be52e2738303eee3c9fdb0d/chrome/browser/prerender/prerender_final_status.h
[modify] https://crrev.com/07afa9f65f71178f9be52e2738303eee3c9fdb0d/chrome/browser/prerender/prerender_manager.cc
[modify] https://crrev.com/07afa9f65f71178f9be52e2738303eee3c9fdb0d/chrome/browser/prerender/prerender_manager.h
[modify] https://crrev.com/07afa9f65f71178f9be52e2738303eee3c9fdb0d/chrome/browser/prerender/prerender_message_filter.cc
[modify] https://crrev.com/07afa9f65f71178f9be52e2738303eee3c9fdb0d/chrome/browser/prerender/prerender_message_filter.h
[modify] https://crrev.com/07afa9f65f71178f9be52e2738303eee3c9fdb0d/chrome/browser/prerender/prerender_nostate_prefetch_browsertest.cc
[modify] https://crrev.com/07afa9f65f71178f9be52e2738303eee3c9fdb0d/chrome/browser/prerender/prerender_test_utils.cc
[modify] https://crrev.com/07afa9f65f71178f9be52e2738303eee3c9fdb0d/chrome/browser/prerender/prerender_test_utils.h
[modify] https://crrev.com/07afa9f65f71178f9be52e2738303eee3c9fdb0d/chrome/common/prerender_messages.h
[modify] https://crrev.com/07afa9f65f71178f9be52e2738303eee3c9fdb0d/chrome/renderer/prerender/prerender_dispatcher.cc
[modify] https://crrev.com/07afa9f65f71178f9be52e2738303eee3c9fdb0d/chrome/renderer/prerender/prerender_dispatcher.h
[modify] https://crrev.com/07afa9f65f71178f9be52e2738303eee3c9fdb0d/third_party/WebKit/Source/core/dom/Document.cpp
[modify] https://crrev.com/07afa9f65f71178f9be52e2738303eee3c9fdb0d/third_party/WebKit/Source/web/tests/PrerenderingTest.cpp
[modify] https://crrev.com/07afa9f65f71178f9be52e2738303eee3c9fdb0d/third_party/WebKit/public/platform/WebPrerenderingSupport.h