AW: repopulate the flags UI if Activity is recreated

This repopulates the Spinners in the Flags UI when the Activity is
recreated, to ensure the Activity and Service/ContentProvider have
consistent state. Without this change, the flags UI would have an empty
map of flag overrides, and would clear most of the Service's flags when
the user toggles the first Spinner.

This moves some the ContentProvider communication logic to a separate
bridge class to be shared by both the dev UI and the embedded WebView
browser process.

TBR=torne@chromium.org

Fixed: 1036538
Test: Manual - toggle flags in the Activity, swipe away the Activity, \
Test: and relaunch to see the UI is restored correctly
Change-Id: Ife42a0633707c9d59e5678483a95f4267fbbe739
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1980857Reviewed-by: Nate Fischer <ntfschr@chromium.org>
Reviewed-by: Shimi Zhang <ctzsm@chromium.org>
Commit-Queue: Nate Fischer <ntfschr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#727523}

android_webview/java/src/org/chromium/android_webview/AwBrowserProcess.java

@@ -371,6 +371,7 @@ public final class AwBrowserProcess {
         });
     }
 
+    // TODO(ntfschr): move this to DeveloperModeUtils in common Java packaage.
     // Quickly determine whether developer mode is enabled.
     public static boolean isDeveloperModeEnabled() {
         final Context context = ContextUtils.getApplicationContext();
@@ -386,6 +387,7 @@ public final class AwBrowserProcess {
         helper.applyFlagOverrides(getFlagOverrides());
     }
 
+    // TODO(ntfschr): move this to DeveloperModeUtils in common Java packaage.
     private static Map<String, Boolean> getFlagOverrides() {
         Map<String, Boolean> flagOverrides = new HashMap<>();
 

android_webview/nonembedded/java/src/org/chromium/android_webview/devui/FlagsActivity.java

@@ -10,6 +10,9 @@ import android.content.ComponentName;
 import android.content.Context;
 import android.content.Intent;
 import android.content.ServiceConnection;
+import android.content.pm.PackageManager;
+import android.database.Cursor;
+import android.net.Uri;
 import android.os.Bundle;
 import android.os.IBinder;
 import android.os.RemoteException;
@@ -25,10 +28,12 @@ import android.widget.Spinner;
 import android.widget.TextView;
 
 import org.chromium.android_webview.common.Flag;
+import org.chromium.android_webview.common.FlagOverrideConstants;
 import org.chromium.android_webview.common.ProductionSupportedFlagList;
 import org.chromium.android_webview.common.services.IDeveloperUiService;
 import org.chromium.android_webview.common.services.ServiceNames;
 import org.chromium.android_webview.devui.util.NavigationMenuHelper;
+import org.chromium.base.ContextUtils;
 import org.chromium.base.Log;
 
 import java.util.HashMap;
@@ -51,7 +56,7 @@ public class FlagsActivity extends Activity {
     };
 
     private WebViewPackageError mDifferentPackageError;
-    private final Map<String, Boolean> mOverriddenFlags = new HashMap<>();
+    private Map<String, Boolean> mOverriddenFlags = new HashMap<>();
     private FlagsListAdapter mListAdapter;
 
     @Override
@@ -66,6 +71,12 @@ public class FlagsActivity extends Activity {
                 + "lose app data or compromise your security or privacy. Enabled features apply to "
                 + "WebViews across all apps on the device.");
 
+        // Restore flag overrides from the service process to repopulate the UI, if developer mode
+        // is enabled.
+        if (isDeveloperModeEnabled(getPackageName())) {
+            mOverriddenFlags = getFlagOverrides(getPackageName());
+        }
+
         mListAdapter = new FlagsListAdapter();
         flagsListView.setAdapter(mListAdapter);
 
@@ -76,10 +87,6 @@ public class FlagsActivity extends Activity {
                 new WebViewPackageError(this, findViewById(R.id.flags_activity_layout));
         // show the dialog once when the activity is created.
         mDifferentPackageError.showDialogIfDifferent();
-
-        // TODO(ntfschr): once there's a way to get the flag overrides out of the service, we should
-        // repopulate the UI based on that data (otherwise, we send an empty map to the service,
-        // which causes the service to stop itself).
     }
 
     @Override
@@ -230,4 +237,62 @@ public class FlagsActivity extends Activity {
         mListAdapter.notifyDataSetChanged();
         sendFlagsToService();
     }
+
+    /**
+     * Quickly determine whether developer mode is enabled. Developer mode is off-by-default.
+     *
+     * <p>This makes no guarantees about which processes are alive, it only indicates whether the
+     * user has stepped in or out of "developer mode." Developer mode may be enabled and the
+     * ContentProvider process may be dead if the user has taken a WebView update since enabling
+     * developer mode.
+     *
+     * <p>TODO(ntfschr): move this to DeveloperModeUtils in common Java packaage.
+     *
+     * @param webViewPackageName the package name of the WebView implementation to fetch the flags
+     *     from (generally this is the current WebView provider).
+     */
+    public static boolean isDeveloperModeEnabled(String webViewPackageName) {
+        final Context context = ContextUtils.getApplicationContext();
+        ComponentName flagOverrideContentProvider =
+                new ComponentName(webViewPackageName, ServiceNames.FLAG_OVERRIDE_CONTENT_PROVIDER);
+        int enabledState =
+                context.getPackageManager().getComponentEnabledSetting(flagOverrideContentProvider);
+        return enabledState == PackageManager.COMPONENT_ENABLED_STATE_ENABLED;
+    }
+
+    /**
+     * Fetch the flag overrides from the developer mode ContentProvider. This should only be called
+     * if {@link #isDeveloperModeEnabled(String}} returns {@code true}, otherwise this may incur
+     * unnecessary IPC or start up processes unnecessarily.
+     *
+     * <p>TODO(ntfschr): move this to DeveloperModeUtils in common Java packaage.
+     *
+     * @param webViewPackageName the package name of the WebView implementation to fetch the flags
+     *     from (generally this is the current WebView provider).
+     */
+    public static Map<String, Boolean> getFlagOverrides(String webViewPackageName) {
+        Map<String, Boolean> flagOverrides = new HashMap<>();
+
+        Uri uri =
+                new Uri.Builder()
+                        .scheme("content")
+                        .authority(webViewPackageName + FlagOverrideConstants.URI_AUTHORITY_SUFFIX)
+                        .path(FlagOverrideConstants.URI_PATH)
+                        .build();
+        final Context appContext = ContextUtils.getApplicationContext();
+        try (Cursor cursor = appContext.getContentResolver().query(uri, /* projection */ null,
+                     /* selection */ null, /* selectionArgs */ null, /* sortOrder */ null)) {
+            assert cursor != null : "ContentProvider doesn't support querying '" + uri + "'";
+            int flagNameColumnIndex =
+                    cursor.getColumnIndexOrThrow(FlagOverrideConstants.FLAG_NAME_COLUMN);
+            int flagStateColumnIndex =
+                    cursor.getColumnIndexOrThrow(FlagOverrideConstants.FLAG_STATE_COLUMN);
+            while (cursor.moveToNext()) {
+                String flagName = cursor.getString(flagNameColumnIndex);
+                boolean flagState = cursor.getInt(flagStateColumnIndex) != 0;
+                flagOverrides.put(flagName, flagState);
+            }
+        }
+        return flagOverrides;
+    }
 }