[LazyParseCSS] Add metrics for total # of rules at 0% and 100% usage

[LazyParseCSS] Add metrics for total # of rules at 0% and 100% usage

Metrics on Android were showing large % of sheets with 100% usage,
that we still lazily parse. This patch will help illuminate if this is an issue
in practice, by logging how much smaller these are than the average 
sheet we lazily parse.

Ideally, these will be small enough that we won't need to add any gating
behavior and we can still lazily parse these, even if they don't need it.

BUG=685623
Review-Url: https://codereview.chromium.org/2687023003
Cr-Commit-Position: refs/heads/master@{#450397}
Committed: https://chromium.googlesource.com/chromium/src/+/146eafbb2d1135f23696e2acca9a9c79cfa9b871

[Charlie Harrison, 2017-02-09 02:15:46]

The CQ bit was checked by csharrison@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-02-09 02:16:15]

Dry run: 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, 2017-02-09 06:30:38]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-02-09 06:30:40]

Dry run: This issue passed the CQ dry run.

[Charlie Harrison, 2017-02-09 13:09:51]

Description was changed from

==========
[LazyParseCSS] Add metrics for total # of rules at 0% and 100% usage

BUG=685623
==========

to

==========
[LazyParseCSS] Add metrics for total # of rules at 0% and 100% usage

Metrics on Android were showing large % of sheets with 100% usage,
that we still lazily parse. This patch will help illuminate if this is an issue
in practice, by logging how much smaller these are than the average 
sheet we lazily parse.

Ideally, these will be small enough that we won't need to add any gating
behavior and we can still lazily parse these, even if they don't need it.

BUG=685623
==========

[Charlie Harrison, 2017-02-09 13:11:10]

csharrison@chromium.org changed reviewers:
+ rune@opera.com

[Charlie Harrison, 2017-02-09 13:11:10]

Hey Rune,
Would you PTAL at this metrics patch?

[rune, 2017-02-10 10:33:52]

lgtm modulo bikeshedding.

You need someone else to stamp tools/ perhaps?

https://codereview.chromium.org/2687023003/diff/1/third_party/WebKit/Source/c...
File third_party/WebKit/Source/core/css/parser/CSSLazyParsingState.cpp (right):

https://codereview.chromium.org/2687023003/diff/1/third_party/WebKit/Source/c...
third_party/WebKit/Source/core/css/parser/CSSLazyParsingState.cpp:28: void
CSSLazyParsingState::finishStrictParsing() {
I was confused by the name. When I see "strict", I think "strict" as opposed to
"quirks" mode. Would something like "initial" or "minimal" be better?

[Charlie Harrison, 2017-02-10 12:49:41]

csharrison@chromium.org changed reviewers:
+ jwd@chromium.org

[Charlie Harrison, 2017-02-10 12:49:42]

Thanks!
+jwd can you review histograms.xml please?

https://codereview.chromium.org/2687023003/diff/1/third_party/WebKit/Source/c...
File third_party/WebKit/Source/core/css/parser/CSSLazyParsingState.cpp (right):

https://codereview.chromium.org/2687023003/diff/1/third_party/WebKit/Source/c...
third_party/WebKit/Source/core/css/parser/CSSLazyParsingState.cpp:28: void
CSSLazyParsingState::finishStrictParsing() {
On 2017/02/10 10:33:52, rune wrote:
> I was confused by the name. When I see "strict", I think "strict" as opposed
to
> "quirks" mode. Would something like "initial" or "minimal" be better?

Done. Changed to "finishInitialParsing".

[jwd, 2017-02-14 15:57:05]

Histograms LGTM

FYI, if you're not aware, the histogram sum reported in the aggregated data is a
true sum for the histogram. This seems like it would be useful for these
metrics.

https://codereview.chromium.org/2687023003/diff/20001/tools/metrics/histogram...
File tools/metrics/histograms/histograms.xml (right):

https://codereview.chromium.org/2687023003/diff/20001/tools/metrics/histogram...
tools/metrics/histograms/histograms.xml:66538: +<histogram
name="Style.TotalLazyRules.FullUsage" units="count">
Not important now, but this could have been defined using the suffixes mechanism
described at the top of this file. No need to change it, but if you ever add
more TotalLazyRules.* histograms, I recommend you switch to that.

[Charlie Harrison, 2017-02-14 16:04:21]

Thanks, yeah I'll certainly move to suffixes in the future if we add more.

[Charlie Harrison, 2017-02-14 16:04:25]

The CQ bit was checked by csharrison@chromium.org

[Charlie Harrison, 2017-02-14 16:04:25]

The patchset sent to the CQ was uploaded after l-g-t-m from rune@opera.com
Link to the patchset: https://codereview.chromium.org/2687023003/#ps20001
(title: "rune review")

[commit-bot: I haz the power, 2017-02-14 16:05:08]

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, 2017-02-14 17:40:39]

CQ is committing da patch.

Bot data: {"patchset_id": 20001, "attempt_start_ts": 1487088265610290,
"parent_rev": "1f2e38edd1f5c21f9c52fb7d718ec87dc9b0b8e1", "commit_rev":
"146eafbb2d1135f23696e2acca9a9c79cfa9b871"}

[commit-bot: I haz the power, 2017-02-14 17:41:11]

Description was changed from

==========
[LazyParseCSS] Add metrics for total # of rules at 0% and 100% usage

Metrics on Android were showing large % of sheets with 100% usage,
that we still lazily parse. This patch will help illuminate if this is an issue
in practice, by logging how much smaller these are than the average 
sheet we lazily parse.

Ideally, these will be small enough that we won't need to add any gating
behavior and we can still lazily parse these, even if they don't need it.

BUG=685623
==========

to

==========
[LazyParseCSS] Add metrics for total # of rules at 0% and 100% usage

Metrics on Android were showing large % of sheets with 100% usage,
that we still lazily parse. This patch will help illuminate if this is an issue
in practice, by logging how much smaller these are than the average 
sheet we lazily parse.

Ideally, these will be small enough that we won't need to add any gating
behavior and we can still lazily parse these, even if they don't need it.

BUG=685623

Review-Url: https://codereview.chromium.org/2687023003
Cr-Commit-Position: refs/heads/master@{#450397}
Committed:
https://chromium.googlesource.com/chromium/src/+/146eafbb2d1135f23696e2acca9a...
==========

[commit-bot: I haz the power, 2017-02-14 17:41:12]

Committed patchset #2 (id:20001) as
https://chromium.googlesource.com/chromium/src/+/146eafbb2d1135f23696e2acca9a...