Adjust the limits for HTMLParsing UMA

The limits for the recently added HTMLParsing UMA metrics were
too low. Adjust them based on UKM numbers indicating the maximum values
seen in practice.

Bug: 1063448
Change-Id: Idb434fdc8fa5ad2d3743338bd9b1397fa0e48815
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2116915
Commit-Queue: Stephen Chenney <schenney@chromium.org>
Reviewed-by: Mason Freed <masonfreed@chromium.org>
Auto-Submit: Stephen Chenney <schenney@chromium.org>
Cr-Commit-Position: refs/heads/master@{#753210}

third_party/blink/renderer/core/html/parser/html_parser_metrics.cc

@@ -45,19 +45,19 @@ void HTMLParserMetrics::AddYieldInterval(base::TimeDelta elapsed_time) {
 }
 
 void HTMLParserMetrics::ReportMetricsAtParseEnd() {
-  // Report the histograms
+  // The various histogram limits were chosen based on initial UKM data.
   UMA_HISTOGRAM_COUNTS_1000("Blink.HTMLParsing.ChunkCount", chunk_count_);
   UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES(
       "Blink.HTMLParsing.ParsingTimeMax", max_parsing_time_,
-      base::TimeDelta::FromMicroseconds(1),
-      base::TimeDelta::FromMilliseconds(100), 100);
-  UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES(
-      "Blink.HTMLParsing.ParsingTimeMin", min_parsing_time_,
-      base::TimeDelta::FromMicroseconds(1),
-      base::TimeDelta::FromMilliseconds(100), 100);
+      base::TimeDelta::FromMicroseconds(1), base::TimeDelta::FromSeconds(100),
+      1000);
+  UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES("Blink.HTMLParsing.ParsingTimeMin",
+                                          min_parsing_time_,
+                                          base::TimeDelta::FromMicroseconds(1),
+                                          base::TimeDelta::FromSeconds(1), 100);
   UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES(
       "Blink.HTMLParsing.ParsingTimeTotal", accumulated_parsing_time_,
-      base::TimeDelta::FromMicroseconds(1), base::TimeDelta::FromSeconds(10),
+      base::TimeDelta::FromMicroseconds(1), base::TimeDelta::FromSeconds(100),
       1000);
   UMA_HISTOGRAM_COUNTS_1M("Blink.HTMLParsing.TokensParsedMax",
                           max_tokens_parsed_);
@@ -70,16 +70,16 @@ void HTMLParserMetrics::ReportMetricsAtParseEnd() {
   if (max_yield_interval_ != base::TimeDelta()) {
     UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES(
         "Blink.HTMLParsing.YieldedTimeMax", max_yield_interval_,
-        base::TimeDelta::FromMicroseconds(1), base::TimeDelta::FromSeconds(1),
-        100);
+        base::TimeDelta::FromMicroseconds(1), base::TimeDelta::FromSeconds(100),
+        1000);
     UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES(
         "Blink.HTMLParsing.YieldedTimeMin", min_yield_interval_,
-        base::TimeDelta::FromMicroseconds(1), base::TimeDelta::FromSeconds(1),
+        base::TimeDelta::FromMicroseconds(1), base::TimeDelta::FromSeconds(10),
         100);
     UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES(
         "Blink.HTMLParsing.YieldedTimeAverage",
         accumulated_yield_intervals_ / yield_count_,
-        base::TimeDelta::FromMicroseconds(1), base::TimeDelta::FromSeconds(1),
+        base::TimeDelta::FromMicroseconds(1), base::TimeDelta::FromSeconds(10),
         100);
   }
 

third_party/blink/renderer/core/html/parser/html_parser_metrics_test.cc

@@ -82,7 +82,10 @@ TEST_F(HTMLParserMetricsTest, ReportSingleChunk) {
   EXPECT_EQ(parsing_time_min_buckets.size(), 1u);
   EXPECT_EQ(parsing_time_total_buckets.size(), 1u);
   EXPECT_GT(parsing_time_max_buckets[0].min, 0);
-  EXPECT_EQ(parsing_time_max_buckets[0], parsing_time_min_buckets[0]);
+  // Parsing time max has more buckets, with more buckets closely spaced at the
+  // low end of time. So the bucket number should be higher than that for
+  // the min value.
+  EXPECT_GT(parsing_time_max_buckets[0].min, parsing_time_min_buckets[0].min);
   // Can't compare total buckets with max/min because different histogram
   // max values mean different bucket widths.
 }
@@ -161,8 +164,8 @@ TEST_F(HTMLParserMetricsTest, HistogramReportsTwoChunks) {
   EXPECT_EQ(yield_time_min_buckets.size(), 1u);
   EXPECT_EQ(yield_time_average_buckets.size(), 1u);
   EXPECT_GT(yield_time_max_buckets[0].min, 0);
-  EXPECT_EQ(yield_time_max_buckets[0], yield_time_min_buckets[0]);
-  EXPECT_EQ(yield_time_max_buckets[0], yield_time_average_buckets[0]);
+  EXPECT_GT(yield_time_max_buckets[0].min, yield_time_min_buckets[0].min);
+  EXPECT_GT(yield_time_max_buckets[0].min, yield_time_average_buckets[0].min);
 }
 
 TEST_F(HTMLParserMetricsTest, UkmStoresValuesCorrectly) {