[AW][Dev-UI] scrollable warning message in flag UI

This puts the flag UI's warning text into the ListView so it can scroll
off screen as the user scrolls down the list of flags. This adds some
complexity because the ListView now supports two different types of
layouts.

This swaps the order of the warning text and the "reset all" button.
This is in order to pin the "reset all" button to the top of the
Fragment.

Fixed: 1059881
Test: Manual - verify the warning text scrolls as expected
Change-Id: Id7afd2b256051d6d7bf5cee18c73592021444194
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2330042
Commit-Queue: Nate Fischer <ntfschr@chromium.org>
Reviewed-by: Hazem Ashmawy <hazems@chromium.org>
Cr-Commit-Position: refs/heads/master@{#795070}

android_webview/nonembedded/java/res_devui/layout/fragment_flags.xml

@@ -14,17 +14,13 @@
     android:paddingStart="8dp"
     android:paddingEnd="8dp">
 
-    <include
-        layout="@layout/flag_ui_warning"
-        android:layout_width="match_parent"
-        android:layout_height="wrap_content"/>
-
     <!--suppress HardcodedText -->
     <Button
         android:text="Reset all to default"
         android:id="@+id/reset_flags_button"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
+        android:layout_marginTop="8dp"
         android:layout_marginBottom="8dp"
         android:textAppearance="?android:attr/textAppearanceMedium"/>
 

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

@@ -24,6 +24,9 @@ import android.widget.ListView;
 import android.widget.Spinner;
 import android.widget.TextView;
 
+import androidx.annotation.IntDef;
+import androidx.annotation.NonNull;
+
 import org.chromium.android_webview.common.DeveloperModeUtils;
 import org.chromium.android_webview.common.Flag;
 import org.chromium.android_webview.common.ProductionSupportedFlagList;
@@ -73,10 +76,6 @@ public class FlagsFragment extends DevUiBaseFragment {
         activity.setTitle("WebView Flags");
 
         ListView flagsListView = view.findViewById(R.id.flags_list);
-        TextView flagsDescriptionView = view.findViewById(R.id.flags_description);
-        flagsDescriptionView.setText("By enabling these features, you could "
-                + "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.
@@ -84,7 +83,13 @@ public class FlagsFragment extends DevUiBaseFragment {
             mOverriddenFlags = DeveloperModeUtils.getFlagOverrides(mContext.getPackageName());
         }
 
-        mListAdapter = new FlagsListAdapter(sortFlagList(ProductionSupportedFlagList.sFlagList));
+        Flag[] sortedFlags = sortFlagList(ProductionSupportedFlagList.sFlagList);
+        Flag[] flagsAndWarningText = new Flag[ProductionSupportedFlagList.sFlagList.length + 1];
+        flagsAndWarningText[0] = null; // the first entry is the warning text
+        for (int i = 0; i < ProductionSupportedFlagList.sFlagList.length; i++) {
+            flagsAndWarningText[i + 1] = sortedFlags[i];
+        }
+        mListAdapter = new FlagsListAdapter(flagsAndWarningText);
         flagsListView.setAdapter(mListAdapter);
 
         Button resetFlagsButton = view.findViewById(R.id.reset_flags_button);
@@ -163,16 +168,22 @@ public class FlagsFragment extends DevUiBaseFragment {
         public void onNothingSelected(AdapterView<?> parent) {}
     }
 
+    @IntDef({LayoutType.WARNING_MESSAGE, LayoutType.TOGGLEABLE_FLAG})
+    private @interface LayoutType {
+        int WARNING_MESSAGE = 0;
+        int TOGGLEABLE_FLAG = 1;
+        int COUNT = 2;
+    }
+
     /**
      * Adapter to create rows of toggleable Flags.
      */
     private class FlagsListAdapter extends ArrayAdapter<Flag> {
-        public FlagsListAdapter(Flag[] sortedFlags) {
-            super(mContext, R.layout.toggleable_flag, sortedFlags);
+        public FlagsListAdapter(Flag[] flagsAndWarningText) {
+            super(mContext, 0, flagsAndWarningText);
         }
 
-        @Override
-        public View getView(int position, View view, ViewGroup parent) {
+        private View getToggleableFlag(@NonNull Flag flag, View view, ViewGroup parent) {
             // If the the old view is already created then reuse it, else create a new one by layout
             // inflation.
             if (view == null) {
@@ -183,7 +194,6 @@ public class FlagsFragment extends DevUiBaseFragment {
             TextView flagDescription = view.findViewById(R.id.flag_description);
             Spinner flagToggle = view.findViewById(R.id.flag_toggle);
 
-            Flag flag = getItem(position);
             String label = flag.getName();
             if (flag.getEnabledStateValue() != null) {
                 label += "=" + flag.getEnabledStateValue();
@@ -203,6 +213,43 @@ public class FlagsFragment extends DevUiBaseFragment {
 
             return view;
         }
+
+        private View getWarningMessage(View view, ViewGroup parent) {
+            // If the the old view is already created then reuse it, else create a new one by layout
+            // inflation.
+            if (view == null) {
+                view = getLayoutInflater().inflate(R.layout.flag_ui_warning, null);
+            }
+
+            TextView flagsDescriptionView = view.findViewById(R.id.flags_description);
+            flagsDescriptionView.setText("By enabling these features, you could "
+                    + "lose app data or compromise your security or privacy. Enabled features "
+                    + "apply to WebViews across all apps on the device.");
+
+            return view;
+        }
+
+        @Override
+        @LayoutType
+        public int getItemViewType(int position) {
+            if (getItem(position) == null) return LayoutType.WARNING_MESSAGE;
+            return LayoutType.TOGGLEABLE_FLAG;
+        }
+
+        @Override
+        public int getViewTypeCount() {
+            return LayoutType.COUNT;
+        }
+
+        @Override
+        public View getView(int position, View view, ViewGroup parent) {
+            Flag flag = getItem(position);
+            if (getItemViewType(position) == LayoutType.WARNING_MESSAGE) {
+                return getWarningMessage(view, parent);
+            } else {
+                return getToggleableFlag(flag, view, parent);
+            }
+        }
     }
 
     /**