Android: Record the number of strong bindings at OOMs

BUG=855037

Change-Id: Ifb2d3298db6cc368ceb5f7ed4de7cf01f412be81
Reviewed-on: https://chromium-review.googlesource.com/1161381Reviewed-by: Bo <boliu@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Siddhartha S <ssid@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581019}

components/crash/content/browser/crash_metrics_reporter_android.cc

@@ -253,6 +253,9 @@ void CrashMetricsReporter::CrashDumpProcessed(
     }
     UMA_HISTOGRAM_ENUMERATION(
         "Stability.Android.StrongBindingOomRemainingBindingState", combo);
+    UMA_HISTOGRAM_EXACT_LINEAR(
+        "Stability.Android.StrongBindingOomRemainingStrongBindingCount",
+        info.remaining_process_with_strong_binding, 20);
   }
 
   ReportLegacyCrashUma(info, has_valid_dump);

tools/metrics/histograms/histograms.xml

@@ -97342,6 +97342,17 @@ uploading your change for review.
   </summary>
 </histogram>
 
+<histogram name="Stability.Android.StrongBindingOomRemainingStrongBindingCount">
+  <owner>boliu@chromium.org</owner>
+  <owner>ssid@chromium.org</owner>
+  <summary>
+    Record the count of strongly bound child services left when a child service
+    with strong binding is OOM killed by Android. Recorded when such a OOM kill
+    is detected by browser. Note this does not distinguish process type, and is
+    for example count both GPU and renderer process.
+  </summary>
+</histogram>
+
 <histogram name="Stability.BadMessageTerminated.Chrome"
     enum="BadMessageReasonChrome">
   <owner>nick@chromium.org</owner>