predictors: Add RedirectStatus histogram + fix redirects related bug.

predictors: Add RedirectStatus histogram + fix redirects related bug.

This CL adds a new enumeration histogram that allows to keep track of success of
redirect predictions in the ResourcePrefetchPredictor.
Also it fixes a bug with incorrect reporting prefetch and prediction accuracy
histograms in presence of redirect. ResourcePrefetchPredictor uses the first url
in the redirect chain to trigger prefetch so it has to use the same url when it
reports accuracy histograms.

BUG=680049
Review-Url: https://codereview.chromium.org/2719533002
Cr-Commit-Position: refs/heads/master@{#453197}
Committed: https://chromium.googlesource.com/chromium/src/+/f82a5a8d7a819348f63dfd94e08901a5808645f1

[alexilin, 2017-02-24 17:24:09]

alexilin@chromium.org changed reviewers:
+ isherman@chromium.org, lizeb@chromium.org

[alexilin, 2017-02-24 17:24:10]

isherman: PTAL at histograms.xml, thanks!

lizeb: everything. There is another bug as well. StartPrefetching and
StopPrefetching could be called with different URLs in presence of redirect. I'd
prefer to do it in a different CL if you don't mind.

https://codereview.chromium.org/2719533002/diff/1/chrome/browser/predictors/r...
File chrome/browser/predictors/resource_prefetch_predictor.cc (left):

https://codereview.chromium.org/2719533002/diff/1/chrome/browser/predictors/r...
chrome/browser/predictors/resource_prefetch_predictor.cc:712: const GURL&
main_frame_url = nav_id_without_timing_info.main_frame_url;
This is a bug that I'm talking about.
We starts prefetch using the first URL in the redirect chain. We need to use
initial_url to get the same prefetch data.
The same thing with prefetcher_stats_. OnPrefetchingFinished will be called with
initial_url.

https://codereview.chromium.org/2719533002/diff/1/chrome/browser/predictors/r...
File chrome/browser/predictors/resource_prefetch_predictor_unittest.cc (left):

https://codereview.chromium.org/2719533002/diff/1/chrome/browser/predictors/r...
chrome/browser/predictors/resource_prefetch_predictor_unittest.cc:227: bool
URLRequestSummaryAreEqual(const URLRequestSummary& lhs,
Removing excess code.

https://codereview.chromium.org/2719533002/diff/1/chrome/browser/predictors/r...
chrome/browser/predictors/resource_prefetch_predictor_unittest.cc:258:
scoped_refptr<StrictMock<MockResourcePrefetchPredictorTables> > mock_tables_;
git cl format couldn't stand it.

[Ilya Sherman, 2017-02-24 21:54:47]

Metrics LGTM % a nit:

https://codereview.chromium.org/2719533002/diff/1/tools/metrics/histograms/hi...
File tools/metrics/histograms/histograms.xml (right):

https://codereview.chromium.org/2719533002/diff/1/tools/metrics/histograms/hi...
tools/metrics/histograms/histograms.xml:55372: +    wrong.
nit: s/wrong/incorrectly

[Benoit L, 2017-02-27 12:05:00]

lgtm, thanks.

[alexilin, 2017-02-27 12:20:44]

The CQ bit was checked by alexilin@chromium.org

[alexilin, 2017-02-27 12:20:44]

The patchset sent to the CQ was uploaded after l-g-t-m from
isherman@chromium.org, lizeb@chromium.org
Link to the patchset: https://codereview.chromium.org/2719533002/#ps40001
(title: "Nit.")

[commit-bot: I haz the power, 2017-02-27 12:20:50]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-02-27 13:15:55]

CQ is committing da patch.

Bot data: {"patchset_id": 40001, "attempt_start_ts": 1488198044376760,
"parent_rev": "e56b2c6b7fd8ce438e9b6925dc5d01c58cde7c68", "commit_rev":
"f82a5a8d7a819348f63dfd94e08901a5808645f1"}

[commit-bot: I haz the power, 2017-02-27 13:16:35]

Description was changed from

==========
predictors: Add RedirectStatus histogram + fix redirects related bug.

This CL adds a new enumeration histogram that allows to keep track of success of
redirect predictions in the ResourcePrefetchPredictor.
Also it fixes a bug with incorrect reporting prefetch and prediction accuracy
histograms in presence of redirect. ResourcePrefetchPredictor uses the first url
in the redirect chain to trigger prefetch so it has to use the same url when it
reports accuracy histograms.

BUG=680049
==========

to

==========
predictors: Add RedirectStatus histogram + fix redirects related bug.

This CL adds a new enumeration histogram that allows to keep track of success of
redirect predictions in the ResourcePrefetchPredictor.
Also it fixes a bug with incorrect reporting prefetch and prediction accuracy
histograms in presence of redirect. ResourcePrefetchPredictor uses the first url
in the redirect chain to trigger prefetch so it has to use the same url when it
reports accuracy histograms.

BUG=680049

Review-Url: https://codereview.chromium.org/2719533002
Cr-Commit-Position: refs/heads/master@{#453197}
Committed:
https://chromium.googlesource.com/chromium/src/+/f82a5a8d7a819348f63dfd94e089...
==========

[commit-bot: I haz the power, 2017-02-27 13:16:36]

Committed patchset #3 (id:40001) as
https://chromium.googlesource.com/chromium/src/+/f82a5a8d7a819348f63dfd94e089...