Enabling sampling of UMA and crash reports on Android.

chrome/android/java/src/org/chromium/chrome/browser/preferences/privacy/PrivacyPreferencesManager.java

Index: chrome/android/java/src/org/chromium/chrome/browser/preferences/privacy/PrivacyPreferencesManager.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/preferences/privacy/PrivacyPreferencesManager.java b/chrome/android/java/src/org/chromium/chrome/browser/preferences/privacy/PrivacyPreferencesManager.java
index cc67d03db34b1e97576af014bacf33add19b263c..ff6455abe9bd9ea1d5be24a951ee62fe54628df0 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/preferences/privacy/PrivacyPreferencesManager.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/preferences/privacy/PrivacyPreferencesManager.java
@@ -26,6 +26,7 @@ public class PrivacyPreferencesManager implements CrashReportingPermissionManage
     static final String PREF_CRASH_DUMP_UPLOAD = "crash_dump_upload";
     static final String PREF_CRASH_DUMP_UPLOAD_NO_CELLULAR = "crash_dump_upload_no_cellular";
     static final String PREF_METRICS_REPORTING = "metrics_reporting";
+    private static final String PREF_METRICS_IN_SAMPLE = "metrics_in_sample";
     private static final String PREF_NETWORK_PREDICTIONS = "network_predictions";
     private static final String PREF_BANDWIDTH_OLD = "prefetch_bandwidth";
     private static final String PREF_BANDWIDTH_NO_CELLULAR_OLD = "prefetch_bandwidth_no_cellular";
@@ -277,6 +278,24 @@ public class PrivacyPreferencesManager implements CrashReportingPermissionManage
     }
 
     /**
+     * Sets whether this client is eligible to send metrics. If they are, and there was user
+     * consent, then metrics and crashes would be reported.
+     */
+    public void setClientInMetricsSample(boolean inSample) {
+        mSharedPreferences.edit().putBoolean(PREF_METRICS_IN_SAMPLE, inSample).apply();
+    }
+
+    /**
+     * Checks whether this client is eligible to send metrics. If they are, and there was user
+     * consent, then metrics and crashes would be reported.
+     *
+     * @returns boolean Whether client is eligible to send metrics.
+     */
+    public boolean isClientInMetricsSample() {
+        return mSharedPreferences.getBoolean(PREF_METRICS_IN_SAMPLE, true);

[Ilya Sherman, 2016/08/23 21:32:17]

Hmm, the default value is true?  That seems riskier than the default value being
false.  Or, am I misunderstanding something?  (Hopefully, the default value case
should actually never be reached.  Is there a way to assert that?)

[jwd, 2016/08/23 23:00:58]

The default is that clients are in sample, so if there is consent, they will
send metrics/crashes. If it's false, we'll potentially lose crashes that occur
early in first-run, before native code is initialized. So, the default value
case is actually intended to be reachable.

[Ilya Sherman, 2016/08/24 05:02:50]

Okay, that makes sense.  Could you please add a brief comment here documenting
that reasoning?

[jwd, 2016/08/24 15:06:27]

Done.

+    }
+
+    /**
      * Sets the crash upload preference, which determines whether crash dumps will be uploaded
      * always, never, or only on wifi.
      *
@@ -326,7 +345,6 @@ public class PrivacyPreferencesManager implements CrashReportingPermissionManage
 
     /**
      * Sets the initial value for whether crash stacks may be uploaded.
-     * This should be called only once, the first time Chrome is launched.

[Ilya Sherman, 2016/08/23 21:32:17]

Hmm, why did you remove this line?  What are the semantics of "init" / "initial"
now?

[jwd, 2016/08/23 23:00:58]

I should change the first line too, and maybe the name...

I removed the line because it's wrong. It IS being called from other places at
the moment, and it's safe to do so in the new on/off uploads preferences world
(as opposed to the on/only on wifi/off old world).

Gayane is going to be doing a cleanup soon to get rid of the old pref related
stuff.

      */
     public void initCrashUploadPreference(boolean allowCrashUpload) {
         SharedPreferences.Editor ed = mSharedPreferences.edit();