Allow recording child process start time histograms up to 3 min

The 99th percentile of this histogram was topping out at the 10sec
allowed by recordTimesHistogram(), so switch these to using
recordMediumTimesHistogram().

Bug: 1150600
Change-Id: I1839f664f137c0347fdcd06875b4ab1eb843016e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2588867Reviewed-by: Bo <boliu@chromium.org>
Reviewed-by: Weilun Shi <sweilun@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Clark DuVall <cduvall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836976}

base/android/java/src/org/chromium/base/process_launcher/ChildProcessService.java

@@ -283,10 +283,12 @@ public class ChildProcessService {
                     // Record process startup time histograms.
                     long startTime =
                             SystemClock.uptimeMillis() - ApiHelperForN.getStartUptimeMillis();
-                    String baseHistogramName = "Android.ChildProcessStartTime";
+                    String baseHistogramName = "Android.ChildProcessStartTimeV2";
                     String suffix = ContextUtils.isIsolatedProcess() ? ".Isolated" : ".NotIsolated";
-                    RecordHistogram.recordTimesHistogram(baseHistogramName + ".All", startTime);
-                    RecordHistogram.recordTimesHistogram(baseHistogramName + suffix, startTime);
+                    RecordHistogram.recordMediumTimesHistogram(
+                            baseHistogramName + ".All", startTime);
+                    RecordHistogram.recordMediumTimesHistogram(
+                            baseHistogramName + suffix, startTime);
                 }
 
                 mDelegate.runMain();

tools/metrics/histograms/histograms_xml/android/histograms.xml

@@ -268,8 +268,27 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
   </summary>
 </histogram>
 
+<histogram name="Android.ChildProcessStartTimeV2{type}" units="ms"
+    expires_after="2021-12-13">
+  <owner>cduvall@chromium.org</owner>
+  <owner>boliu@chromium.org</owner>
+  <summary>
+    Measures time from {type} child process starts to right before main. Only
+    recorded on Android N+.
+  </summary>
+  <token key="type">
+    <variant name=".All" summary="all"/>
+    <variant name=".Isolated" summary="isolated"/>
+    <variant name=".NotIsolated" summary="non-isolated"/>
+  </token>
+</histogram>
+
 <histogram name="Android.ChildProcessStartTime{type}" units="ms"
     expires_after="2021-09-18">
+  <obsolete>
+    Removed in December 2020, use Android.ChildProcessStartTimeV2.* instead
+    which allows timings up to 3 min.
+  </obsolete>
   <owner>cduvall@chromium.org</owner>
   <owner>boliu@chromium.org</owner>
   <summary>