🤝 Use CachedHistogram for BrowserServicesMetrics.

Bug: 896201
Change-Id: I107f2ec40f1bd0ed2e33799afb4f33707caa86f4
Reviewed-on: https://chromium-review.googlesource.com/c/1286654
Commit-Queue: Peter Conn <peconn@chromium.org>
Reviewed-by: Michael van Ouwerkerk <mvanouwerkerk@chromium.org>
Reviewed-by: agrieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600413}

base/android/java/src/org/chromium/base/metrics/CachedMetrics.java

@@ -158,7 +158,7 @@ public class CachedMetrics {
     /** Caches a set of times histogram samples. */
     public static class TimesHistogramSample extends CachedMetric {
         private final List<Long> mSamples = new ArrayList<Long>();
-        private final TimeUnit mTimeUnit;
+        protected final TimeUnit mTimeUnit;
 
         public TimesHistogramSample(String histogramName, TimeUnit timeUnit) {
             super(histogramName);
@@ -177,7 +177,7 @@ public class CachedMetrics {
             }
         }
 
-        private void recordWithNative(long sample) {
+        protected void recordWithNative(long sample) {
             RecordHistogram.recordTimesHistogram(mName, sample, mTimeUnit);
         }
 
@@ -190,6 +190,21 @@ public class CachedMetrics {
         }
     }
 
+    /**
+     * Caches a set of times histogram samples, calls
+     * {@link RecordHistogram#recordMediumTimesHistogram(String, long, TimeUnit)}.
+     */
+    public static class MediumTimesHistogramSample extends TimesHistogramSample {
+        public MediumTimesHistogramSample(String histogramName, TimeUnit timeUnit) {
+            super(histogramName, timeUnit);
+        }
+
+        @Override
+        protected void recordWithNative(long sample) {
+            RecordHistogram.recordMediumTimesHistogram(mName, sample, mTimeUnit);
+        }
+    }
+
     /** Caches a set of boolean histogram samples. */
     public static class BooleanHistogramSample extends CachedMetric {
         private final List<Boolean> mSamples = new ArrayList<Boolean>();

chrome/android/java/src/org/chromium/chrome/browser/browserservices/BrowserServicesMetrics.java

@@ -7,6 +7,7 @@ package org.chromium.chrome.browser.browserservices;
 import android.os.SystemClock;
 import android.support.annotation.IntDef;
 
+import org.chromium.base.metrics.CachedMetrics;
 import org.chromium.base.metrics.RecordHistogram;
 import org.chromium.base.metrics.RecordUserAction;
 
@@ -93,8 +94,9 @@ public class BrowserServicesMetrics {
 
         @Override
         public void close() {
-            RecordHistogram.recordMediumTimesHistogram(
-                    mMetric, now() - mStart, TimeUnit.MILLISECONDS);
+            // Use {@link CachedMetrics} so this can be called before native is loaded.
+            new CachedMetrics.MediumTimesHistogramSample(mMetric, TimeUnit.MILLISECONDS)
+                    .record(now() - mStart);
         }
     }