[WebLayer] Encapsulate Minimal UI in PaymentUiService

MinimalUi is the implementation details of PaymentUiService and so
should not be exposed to the payment request service. This CL
encapsulate the MinimalUI logic in PaymentUiService so that
PaymentUiService no longer provides the MinimalUICoordinator instance.

Bug: 1155582
Change-Id: Ica49ae9190248d400f29ef8102c9a4394356ad85
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2575342
Commit-Queue: Liquan (Max) Gu <maxlg@chromium.org>
Reviewed-by: Rouslan Solomakhin <rouslan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#834023}

chrome/android/java/src/org/chromium/chrome/browser/payments/ChromePaymentRequestService.java

@@ -10,7 +10,6 @@ import androidx.annotation.Nullable;
 import androidx.collection.ArrayMap;
 
 import org.chromium.base.metrics.RecordHistogram;
-import org.chromium.chrome.R;
 import org.chromium.chrome.browser.app.ChromeActivity;
 import org.chromium.chrome.browser.autofill.PersonalDataManager;
 import org.chromium.chrome.browser.payments.handler.PaymentHandlerCoordinator;
@@ -671,10 +670,9 @@ public class ChromePaymentRequestService
     // Implements BrowserPaymentRequest:
     @Override
     public void onInstrumentDetailsError(String errorMessage) {
-        if (mPaymentUiService.getMinimalUI() != null) {
+        if (mPaymentUiService.isShowingMinimalUi()) {
             mJourneyLogger.setAborted(AbortReason.ABORTED_BY_USER);
-            mPaymentUiService.getMinimalUI().showErrorAndClose(
-                    /*observer=*/this::close, R.string.payments_error_message);
+            mPaymentUiService.closeMinimalUiOnError(this::close);
             return;
         }
 

chrome/android/java/src/org/chromium/chrome/browser/payments/ui/PaymentUiService.java

@@ -443,9 +443,20 @@ public class PaymentUiService implements SettingsAutofillAndPaymentsObserver.Obs
         return mHaveRequestedAutofillData;
     }
 
-    /** @return The minimal UI coordinator. */
-    public MinimalUICoordinator getMinimalUI() {
-        return mMinimalUi;
+    /**
+     * Closes the minimal UI and shows an error message, called only when isShowingMinimalUi()
+     * returns true.
+     * @param onClosed Called when the minimal UI is closed.
+     */
+    public void closeMinimalUiOnError(Runnable onClosed) {
+        assert mMinimalUi != null;
+        mMinimalUi.showErrorAndClose(
+                /*observer=*/onClosed::run, R.string.payments_error_message);
+    }
+
+    /** @return Whether the minimal UI is showing. */
+    public boolean isShowingMinimalUi() {
+        return mMinimalUi != null;
     }
 
     // Implements PaymentUiServiceTestInterface: