[M109] Binding Manager Connection Limit: Additional Metrics

Additional metric recording:
* Waived binding OOM count.
* Number of times bindings are dropped from hitting the BindingManager
  max connection limit.

These metrics should help inform whether the BindingManagerConnection
limit experiment makes sense to launch.

(cherry picked from commit 1b56458)

Bug: 1385812
Change-Id: I55a278f5f6a43ca08756674b8f4677efec0902ac
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4031089
Commit-Queue: Calder Kitagawa <ckitagawa@chromium.org>
Reviewed-by: Mark Mentovai <mark@chromium.org>
Reviewed-by: Bo Liu <boliu@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#1073004}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4037287
Auto-Submit: Calder Kitagawa <ckitagawa@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
Commit-Queue: Yaron Friedman <yfriedman@chromium.org>
Cr-Commit-Position: refs/branch-heads/5414@{chromium#145}
Cr-Branched-From: 4417ee5-refs/heads/main@{#1070088}

components/crash/content/browser/crash_metrics_reporter_android.cc

@@ -186,7 +186,14 @@ void CrashMetricsReporter::ChildProcessExited(
       // the bindings are updated later than visibility on web contents.
       switch (info.binding_state) {
         case base::android::ChildBindingState::UNBOUND:
+          break;
         case base::android::ChildBindingState::WAIVED:
+          if (!intentional_kill && !info.normal_termination) {
+            ReportCrashCount(
+                ProcessedCrashCounts::
+                    kRendererForegroundInvisibleWithWaivedBindingOom,
+                &reported_counts);
+          }
           break;
         case base::android::ChildBindingState::STRONG:
           if (intentional_kill || info.normal_termination) {

components/crash/content/browser/crash_metrics_reporter_android.h

@@ -55,7 +55,8 @@ class CrashMetricsReporter {
     kRendererForegroundInvisibleWithVisibleBindingOom = 21,
     kRendererForegroundInvisibleWithNotPerceptibleBindingKilled = 22,
     kRendererForegroundInvisibleWithNotPerceptibleBindingOom = 23,
-    kMaxValue = kRendererForegroundInvisibleWithNotPerceptibleBindingOom
+    kRendererForegroundInvisibleWithWaivedBindingOom = 24,
+    kMaxValue = kRendererForegroundInvisibleWithWaivedBindingOom
   };
   using ReportedCrashTypeSet = base::flat_set<ProcessedCrashCounts>;
 

content/public/android/java/src/org/chromium/content/browser/BindingManager.java

@@ -12,6 +12,7 @@
 import androidx.collection.ArraySet;
 
 import org.chromium.base.Log;
+import org.chromium.base.metrics.RecordHistogram;
 import org.chromium.base.process_launcher.ChildProcessConnection;
 import org.chromium.content_public.browser.ContentFeatureList;
 import org.chromium.content_public.common.ContentFeatures;
@@ -48,6 +49,8 @@ class BindingManager implements ComponentCallbacks2 {
     // by BindingManager.
     private ChildProcessConnection mWaivedConnection;
 
+    private int mConnectionsDroppedDueToMaxSize;
+
     @Override
     public void onTrimMemory(final int level) {
         LauncherThread.post(new Runnable() {
@@ -142,6 +145,12 @@ private void ensureLowestRankIsWaived() {
      */
     void onSentToBackground() {
         assert LauncherThread.runningOnLauncherThread();
+
+        RecordHistogram.recordCount1000Histogram(
+                "Android.BindingManger.ConnectionsDroppedDueToMaxSize",
+                mConnectionsDroppedDueToMaxSize);
+        mConnectionsDroppedDueToMaxSize = 0;
+
         if (mConnections.isEmpty()) return;
         LauncherThread.postDelayed(mDelayedClearer, BINDING_POOL_CLEARER_DELAY_MILLIS);
     }
@@ -243,6 +252,7 @@ public void addConnection(ChildProcessConnection connection) {
         addBinding(connection);
 
         if (mMaxSize != NO_MAX_SIZE && mConnections.size() == mMaxSize + 1) {
+            mConnectionsDroppedDueToMaxSize++;
             removeOldConnections(1);
             ensureLowestRankIsWaived();
         }

tools/metrics/histograms/enums.xml

@@ -2447,6 +2447,8 @@ Unknown properties are collapsed to zero. -->
   <int value="23"
       label="Invisible renderer in foreground app with not perceptible
              binding oom"/>
+  <int value="24"
+      label="Invisible renderer in foreground app with waived binding oom"/>
 </enum>
 
 <enum name="AndroidProcessedMinidumps">

tools/metrics/histograms/metadata/android/histograms.xml

@@ -824,6 +824,18 @@ chromium-metrics-reviews@google.com.
   </summary>
 </histogram>
 
+<histogram name="Android.BindingManger.ConnectionsDroppedDueToMaxSize"
+    units="connections" expires_after="2023-04-16">
+  <owner>ckitagawa@chromium.org</owner>
+  <owner>yfriedman@chromium.org</owner>
+  <summary>
+    Records the total number of BindingManager bindings to
+    ChildProcessConnections that were dropped due to the BindingManager reaching
+    the connection limit. This value accumulates while the app is running and is
+    emitted upong the app being backgrounded at which time the counter is reset.
+  </summary>
+</histogram>
+
 <histogram name="Android.BiometricAuth.AuthRequester"
     enum="BiometricAuthRequester" expires_after="M112">
   <owner>ioanap@chromium.org</owner>