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

Using onCreate and onDestroy means that the user can go into the Google
Activity Controls or Sync settings subpages without triggering sync.
Note that leaving the sync page will still cause sync to start, but at
that point it seems safe to assume the settings are good.

BUG=613340

Review-Url: https://codereview.chromium.org/1988133005
Cr-Commit-Position: refs/heads/master@{#395081}

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 void onPause() {
         }
     }
 
+    @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 void onSignOutDialogDismissed(boolean signOutClicked) {
     @Override
     public void syncStateChanged() {
         SyncPreference pref = (SyncPreference) findPreference(PREF_SYNC_SETTINGS);
-        pref.updateSyncSummaryAndIcon();
+        if (pref != null) {
+            pref.updateSyncSummaryAndIcon();
+        }
 
         // TODO(crbug/557784): Show notification for sync error
     }