[AW][Dev-UI] adjust padding for consistency

No change to logic. This adjusts padding and margins for consistency
with the crash UI (most stuff should be 8dp now).

This also splits the warning message into its own layout file. This will
be necessary for a follow-up change to move the warning text into the
ListView so it can be scrolled off screen.

Bug: 1111172
Test: Manual
Change-Id: I8bf87c633ec6fc8cc0aa85f581e9825c6a9dff2b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2330291Reviewed-by: Hazem Ashmawy <hazems@chromium.org>
Commit-Queue: Nate Fischer <ntfschr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#795047}

android_webview/nonembedded/BUILD.gn

@@ -140,6 +140,7 @@ android_resources("devui_resources") {
     "java/res_devui/layout/crashes_list_item_body.xml",
     "java/res_devui/layout/crashes_list_item_header.xml",
     "java/res_devui/layout/flag_states.xml",
+    "java/res_devui/layout/flag_ui_warning.xml",
     "java/res_devui/layout/fragment_crashes_list.xml",
     "java/res_devui/layout/fragment_flags.xml",
     "java/res_devui/layout/fragment_home.xml",

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

+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Copyright 2020 The Chromium Authors. All rights reserved.  Use of this
+  source code is governed by a BSD-style license that can be found in the
+  LICENSE file.
+-->
+
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/flag_ui_warning"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:orientation="vertical"
+    android:paddingTop="8dp"
+    android:paddingBottom="8dp">
+
+    <!--suppress HardcodedText -->
+    <TextView
+        android:id="@+id/flags_warning"
+        android:text="WARNING: EXPERIMENTAL FEATURES AHEAD!"
+        android:textColor="@color/error_red"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_marginBottom="8dp"
+        android:textAppearance="?android:attr/textAppearanceLarge"/>
+
+    <TextView
+        android:id="@+id/flags_description"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:textAppearance="?android:attr/textAppearanceMedium"/>
+
+</LinearLayout>

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

@@ -11,26 +11,13 @@
     android:orientation="vertical"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
-    android:padding="10dp">
+    android:paddingStart="8dp"
+    android:paddingEnd="8dp">
 
-    <!--suppress HardcodedText -->
-    <TextView
-        android:id="@+id/flags_warning"
-        android:text="WARNING: EXPERIMENTAL FEATURES AHEAD!"
-        android:textColor="@color/error_red"
-        android:layout_width="match_parent"
-        android:layout_height="wrap_content"
-        android:paddingBottom="5dp"
-        android:paddingTop="5dp"
-        android:textAppearance="?android:attr/textAppearanceLarge"/>
-
-    <TextView
-        android:id="@+id/flags_description"
+    <include
+        layout="@layout/flag_ui_warning"
         android:layout_width="match_parent"
-        android:layout_height="wrap_content"
-        android:paddingBottom="5dp"
-        android:paddingTop="5dp"
-        android:textAppearance="?android:attr/textAppearanceMedium"/>
+        android:layout_height="wrap_content"/>
 
     <!--suppress HardcodedText -->
     <Button
@@ -38,7 +25,7 @@
         android:id="@+id/reset_flags_button"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
-        android:layout_marginBottom="5dp"
+        android:layout_marginBottom="8dp"
         android:textAppearance="?android:attr/textAppearanceMedium"/>
 
     <!-- horizontal divider -->

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

@@ -10,7 +10,6 @@
     android:id="@+id/toggleable_flag"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
-    android:layout_marginTop="15dp"
     android:orientation="vertical">
 
     <!-- A compound drawable will be populated at runtime, but it's OK to configure drawablePadding now. -->
@@ -22,8 +21,8 @@
         android:textStyle="bold"
         android:textAppearance="?android:attr/textAppearanceMedium"
         android:drawablePadding="4dp"
-        android:paddingBottom="2dp"
-        android:paddingTop="2dp" />
+        android:paddingTop="8dp"
+        android:paddingBottom="8dp"/>
 
     <TextView
         android:id="@+id/flag_description"