[Sync] Ensure the user has a chance to change their settings on Android.

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

Index: chrome/android/java/src/org/chromium/chrome/browser/signin/AccountManagementFragment.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/signin/AccountManagementFragment.java b/chrome/android/java/src/org/chromium/chrome/browser/signin/AccountManagementFragment.java
index 62deb41a6c885e3b68ab02f5e6d64c4eb929258d..915deb2f536eb8592e5c089bbb7f886075894fc7 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/signin/AccountManagementFragment.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/signin/AccountManagementFragment.java
@@ -119,6 +119,13 @@ public class AccountManagementFragment extends PreferenceFragment
     public void onCreate(Bundle savedState) {
         super.onCreate(savedState);
 
+        // Prevent sync from starting if it hasn't already to give the user a chance to change
+        // their sync settings.
+        ProfileSyncService syncService = ProfileSyncService.get();
+        if (syncService != null) {
+            syncService.setSetupInProgress(true);
+        }
+
         mGaiaServiceType = AccountManagementScreenHelper.GAIA_SERVICE_TYPE_NONE;
         if (getArguments() != null) {
             mGaiaServiceType =
@@ -156,6 +163,17 @@ public class AccountManagementFragment extends PreferenceFragment
         }
     }
 
+    @Override
+    public void onDestroy() {
+        super.onDestroy();
+
+        // Allow sync to begin syncing if it hasn't yet.
+        ProfileSyncService syncService = ProfileSyncService.get();
+        if (syncService != null) {
+            syncService.setSetupInProgress(false);
+        }
+    }
+
     /**
      * Initiate fetching the user accounts data (images and the full name).
      * Fetched data will be sent to observers of ProfileDownloader.
@@ -489,7 +507,9 @@ public class AccountManagementFragment extends PreferenceFragment
     @Override
     public void syncStateChanged() {
         SyncPreference pref = (SyncPreference) findPreference(PREF_SYNC_SETTINGS);
-        pref.updateSyncSummaryAndIcon();
+        if (pref != null) {

[gogerald1, 2016/05/20 13:10:19]

Curious, under what circumstance this could be null?

[maxbogue, 2016/05/20 15:53:00]

It's always null before the addPreferencesFromResource() call in update() in
onResume(). Since setting setupInProgress to true triggers syncStateChanged(), I
was hitting a NullPointerException 100% of the time in manual testing.

+            pref.updateSyncSummaryAndIcon();
+        }
 
         // TODO(crbug/557784): Show notification for sync error
     }