[Signin][Android] Move AccountPickerMediator.start/stop to ctor/destroy

This CL replaces the AccountPickerMediator.start()/stop() methods
to its constructor and destroy().

Bug: 1075880
Change-Id: I9dc3bf4b7af74813889e33e798165ffaa802e30b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2193683
Commit-Queue: Alice Wang <aliceywang@chromium.org>
Reviewed-by: Boris Sazonov <bsazonov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#768806}

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

@@ -44,21 +44,6 @@ public class AccountPickerDialogFragment extends DialogFragment {
         return result;
     }
 
-    @Override
-    public void onStart() {
-        super.onStart();
-        // TODO(https://crbug.com/1075880):
-        // Investigate move this method to account picker mediator ctor
-        // and stop() to mediator.destroy()
-        mCoordinator.start();
-    }
-
-    @Override
-    public void onStop() {
-        super.onStop();
-        mCoordinator.stop();
-    }
-
     @Override
     @NonNull
     public Dialog onCreateDialog(Bundle savedInstanceState) {
@@ -76,6 +61,12 @@ public class AccountPickerDialogFragment extends DialogFragment {
                 .create();
     }
 
+    @Override
+    public void onDestroy() {
+        super.onDestroy();
+        mCoordinator.destroy();
+    }
+
     /**
      * Updates the selected account.
      * @param selectedAccountName The name of the account that should be marked as selected.

chrome/android/java/src/org/chromium/chrome/browser/signin/account_picker/AccountPickerCoordinator.java

@@ -64,17 +64,10 @@ public class AccountPickerCoordinator {
     }
 
     /**
-     * Starts the coordinator.
+     * Destroys the resources used by the coordinator.
      */
-    public void start() {
-        mMediator.start();
-    }
-
-    /**
-     * Stops the coordinator.
-     */
-    public void stop() {
-        mMediator.stop();
+    public void destroy() {
+        mMediator.destroy();
     }
 
     /**

chrome/android/java/src/org/chromium/chrome/browser/signin/account_picker/AccountPickerMediator.java

@@ -50,21 +50,16 @@ class AccountPickerMediator {
                 context, context.getResources().getDimensionPixelSize(R.dimen.user_picture_size));
         mSelectedAccountName = selectedAccountName;
         mAccountManagerFacade = AccountManagerFacadeProvider.getInstance();
-    }
 
-    /**
-     * Starts the mediator.
-     * TODO(https://crbug.com/1075880):
-     * Investigate move this method to account picker mediator ctor
-     * and stop() to mediator.destroy()
-     */
-    void start() {
         mAccountManagerFacade.addObserver(mAccountsChangeObserver);
         mProfileDataCache.addObserver(mProfileDataObserver);
         updateAccounts();
     }
 
-    void stop() {
+    /**
+     * Unregisters the observers used by the mediator.
+     */
+    void destroy() {
         mProfileDataCache.removeObserver(mProfileDataObserver);
         mAccountManagerFacade.removeObserver(mAccountsChangeObserver);
     }