Patch to add feature flag: https://codereview.chromium.org/2014183002/

Finch experiment: cl/123313061

(The above CL also assigns an id to the experiment so its impact can be monitored on the server side too.)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5fb28c944ab8cec3e7b1ab0ca866fbc7e242717f

commit 5fb28c944ab8cec3e7b1ab0ca866fbc7e242717f
Author: skyostil <skyostil@chromium.org>
Date: Fri May 27 09:24:44 2016

Add a feature flag for enabling rendering pipeline throttling

Add a feature flag for rendering pipeline throttling so we can evaluate
its impact using a Finch experiment.

BUG= 487937 , 614983 

Review-Url: https://codereview.chromium.org/2014183002
Cr-Commit-Position: refs/heads/master@{#396428}

[modify] https://crrev.com/5fb28c944ab8cec3e7b1ab0ca866fbc7e242717f/content/child/runtime_features.cc
[modify] https://crrev.com/5fb28c944ab8cec3e7b1ab0ca866fbc7e242717f/content/public/common/content_features.cc
[modify] https://crrev.com/5fb28c944ab8cec3e7b1ab0ca866fbc7e242717f/content/public/common/content_features.h
[modify] https://crrev.com/5fb28c944ab8cec3e7b1ab0ca866fbc7e242717f/third_party/WebKit/Source/web/WebRuntimeFeatures.cpp
[modify] https://crrev.com/5fb28c944ab8cec3e7b1ab0ca866fbc7e242717f/third_party/WebKit/public/web/WebRuntimeFeatures.h

Requesting to merge the feature flag to M52.

1. Is there a launch bug associated to this feature?
2. Approved by Launch Review team?
3. Is it safe to merge before baking in canary?

Your change meets the bar and is auto-approved for M52 (branch: 2743)

Yes, there is a launch bug: https://bugs.chromium.org/p/chromium/issues/detail?id=516640

FWIW this feature flag is needed in M52 for turning the feature *off* via a Finch experiment. The feature itself is already there in M52.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/30eaebb30490917efb80e7ebd4a82be301efb98b

commit 30eaebb30490917efb80e7ebd4a82be301efb98b
Author: Sami Kyostila <skyostil@chromium.org>
Date: Tue May 31 09:41:22 2016

Add a feature flag for enabling rendering pipeline throttling

Add a feature flag for rendering pipeline throttling so we can evaluate
its impact using a Finch experiment.

BUG= 487937 , 614983 

Review-Url: https://codereview.chromium.org/2014183002
Cr-Commit-Position: refs/heads/master@{#396428}
(cherry picked from commit 5fb28c944ab8cec3e7b1ab0ca866fbc7e242717f)

Review URL: https://codereview.chromium.org/2028563002 .

Cr-Commit-Position: refs/branch-heads/2743@{#137}
Cr-Branched-From: 2b3ae3b8090361f8af5a611712fc1a5ab2de53cb-refs/heads/master@{#394939}

[modify] https://crrev.com/30eaebb30490917efb80e7ebd4a82be301efb98b/content/child/runtime_features.cc
[modify] https://crrev.com/30eaebb30490917efb80e7ebd4a82be301efb98b/content/public/common/content_features.cc
[modify] https://crrev.com/30eaebb30490917efb80e7ebd4a82be301efb98b/content/public/common/content_features.h
[modify] https://crrev.com/30eaebb30490917efb80e7ebd4a82be301efb98b/third_party/WebKit/Source/web/WebRuntimeFeatures.cpp
[modify] https://crrev.com/30eaebb30490917efb80e7ebd4a82be301efb98b/third_party/WebKit/public/web/WebRuntimeFeatures.h