Upstream changes for android signin promo

1. add uma metrics related to the new android signin promo
2. add a method to SigninManager to get the finch experiment for promo

Downstream changes at https://chrome-internal-review.googlesource.com/#/c/175857/

BUG=406614
TBR=rogerta@chromium.org

Review URL: https://codereview.chromium.org/568603002

Cr-Commit-Position: refs/heads/master@{#294682}

chrome/android/java/src/org/chromium/chrome/browser/signin/SigninManager.java

@@ -16,6 +16,7 @@ import android.util.Log;
 import org.chromium.base.ActivityState;
 import org.chromium.base.ApplicationStatus;
 import org.chromium.base.CalledByNative;
+import org.chromium.base.FieldTrialList;
 import org.chromium.base.ObserverList;
 import org.chromium.base.ThreadUtils;
 import org.chromium.chrome.R;
@@ -400,6 +401,22 @@ public class SigninManager {
         return nativeIsNewProfileManagementEnabled();
     }
 
+    /**
+     * @return Experiment group for the android signin promo that the current user falls into.
+     * -1 if the sigin promo experiment is disabled, otherwise an integer between 0 and 7.
+     * TODO(guohui): instead of group names, it is better to use experiment params to control
+     * the variations.
+     */
+    public static int getAndroidSigninPromoExperimentGroup() {
+        String fieldTrialValue =
+                FieldTrialList.findFullName("AndroidSigninPromo");
+        try {
+            return Integer.parseInt(fieldTrialValue);
+        } catch (NumberFormatException ex) {
+            return -1;
+        }
+    }
+
     @CalledByNative
     private void onSigninAllowedByPolicyChanged(boolean newSigninAllowedByPolicy) {
         mSigninAllowedByPolicy = newSigninAllowedByPolicy;

chrome/browser/signin/signin_promo.h

@@ -43,6 +43,26 @@ enum Source {
   SOURCE_UNKNOWN, // This must be last.
 };
 
+// Enum values used for Android signin promo actions.
+enum AndroidSigninPromoAction {
+  // The promo was enabled.
+  HISTOGRAM_ANDROID_SIGNIN_PROMO_ENABLED = 0,
+
+  // The promo was shown.
+  HISTOGRAM_ANDROID_SIGNIN_PROMO_SHOWN,
+
+  // The promo was declined.
+  HISTOGRAM_ANDROID_SIGNIN_PROMO_DECLINED,
+
+  // The promo was accepted.
+  HISTOGRAM_ANDROID_SIGNIN_PROMO_ACCEPTED,
+
+  // The promo was accepted and user clicked the settings link.
+  HISTOGRAM_ANDROID_SIGNIN_PROMO_ACCEPTED_WITH_ADVANCED,
+
+  HISTOGRAM_ANDROID_SIGNIN_PROMO_MAX,
+};
+
 // Returns true if the sign in promo should be visible.
 // |profile| is the profile of the tab the promo would be shown on.
 bool ShouldShowPromo(Profile* profile);

tools/metrics/histograms/histograms.xml

@@ -29372,6 +29372,11 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Signin.AndroidSigninPromo" enum="AndroidSigninPromoAction">
+  <owner>guohui@chromium.org</owner>
+  <summary>Track how a user interfacts with the android signin promo.</summary>
+</histogram>
+
 <histogram name="Signin.DuringFirstRun">
   <owner>mlerman@chromium.org</owner>
   <summary>
@@ -37718,6 +37723,23 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <int value="3" label="LowMemory"/>
 </enum>
 
+<enum name="AndroidSigninPromoAction" type="int">
+  <int value="0" label="Promo enabled">
+    The Android signin promo was enabled to show on next startup.
+  </int>
+  <int value="1" label="Promo shown">The Android signin promo was shown.</int>
+  <int value="2" label="Promo declined">
+    User declined the Android signin promo.
+  </int>
+  <int value="3" label="Promo accepted">
+    User completed signin through the Android signin promo flow successfully.
+  </int>
+  <int value="4" label="Promo accepted with advanced settings">
+    User completed signin through the Android signin promo flow successfully and
+    chose to configure sync settings.
+  </int>
+</enum>
+
 <enum name="AndroidTabCloseUndoToastEvent" type="int">
   <int value="0" label="Undo Shown (Cold)"/>
   <int value="1" label="Undo Shown (Warm)"/>