[webview] Add dark mode support to webview shell

This adds force dark setting menu items, and modifies the shell theme
sufficiently to allow FORCE_DARK_AUTO to work. Apps must opt in to force
darkening, and must have a theme that is not already "dark", so the
AppCompat.DayNight theme must be configured as such.

Bug: 947324
Change-Id: Ib40af5e3817d91fd497925e58689d9c0fc4f55a6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1899613
Commit-Queue: Tobias Sargeant <tobiasjs@chromium.org>
Reviewed-by: Tim Volodine <timvolodine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#715731}

android_webview/tools/system_webview_shell/BUILD.gn

@@ -34,7 +34,7 @@ android_apk("system_webview_shell_apk") {
     "apk/src/org/chromium/webview_shell/WebViewTracingActivity.java",
   ]
   android_manifest = "apk/AndroidManifest.xml"
-  target_sdk_version = 28
+  target_sdk_version = 29
   deps = [
     ":system_webview_shell_apk_resources",
     "//base:base_java",

android_webview/tools/system_webview_shell/apk/res/menu/main_menu.xml

@@ -11,6 +11,14 @@
     <item android:id="@+id/menu_enable_tracing"
           android:checkable="true"
           android:title="@string/menu_enable_tracing"/>
+    <group android:checkableBehavior="single">
+        <item android:id="@+id/menu_force_dark_off"
+              android:title="@string/menu_force_dark_off"/>
+        <item android:id="@+id/menu_force_dark_auto"
+              android:title="@string/menu_force_dark_auto"/>
+        <item android:id="@+id/menu_force_dark_on"
+              android:title="@string/menu_force_dark_on"/>
+    </group>
     <item android:id="@+id/menu_print"
           android:title="@string/menu_print"/>
     <item android:id="@+id/start_animation_activity"

android_webview/tools/system_webview_shell/apk/res/values-v29/styles.xml

+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright 2019 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. -->
+
+<resources>
+  <style name="ShellTheme" parent="Theme.AppCompat.DayNight.NoActionBar">
+    <item name="android:forceDarkAllowed">true</item>
+    <item name="android:isLightTheme">true</item>
+  </style>
+</resources>

android_webview/tools/system_webview_shell/apk/res/values/strings.xml

@@ -17,6 +17,9 @@
     <string name="menu_reset_webview">Destroy and create new WebView</string>
     <string name="menu_clear_cache">Clear cache</string>
     <string name="menu_enable_tracing">Enable tracing</string>
+    <string name="menu_force_dark_off">Force Dark Off</string>
+    <string name="menu_force_dark_auto">Force Dark Auto</string>
+    <string name="menu_force_dark_on">Force Dark On</string>
     <string name="menu_start_animation_activity">Animation test</string>
     <string name="menu_print">Print</string>
     <string name="menu_about">About WebView</string>

android_webview/tools/system_webview_shell/apk/src/org/chromium/webview_shell/WebViewBrowserActivity.java

@@ -514,6 +514,11 @@ public class WebViewBrowserActivity extends AppCompatActivity {
         if (Build.VERSION.SDK_INT < Build.VERSION_CODES.P) {
             menu.findItem(R.id.menu_enable_tracing).setEnabled(false);
         }
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.Q) {
+            menu.findItem(R.id.menu_force_dark_off).setEnabled(false);
+            menu.findItem(R.id.menu_force_dark_auto).setEnabled(false);
+            menu.findItem(R.id.menu_force_dark_on).setEnabled(false);
+        }
         return true;
     }
 
@@ -522,6 +527,20 @@ public class WebViewBrowserActivity extends AppCompatActivity {
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
             menu.findItem(R.id.menu_enable_tracing).setChecked(mEnableTracing);
         }
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
+            int fdState = mWebView.getSettings().getForceDark();
+            switch (fdState) {
+                case WebSettings.FORCE_DARK_OFF:
+                    menu.findItem(R.id.menu_force_dark_off).setChecked(true);
+                    break;
+                case WebSettings.FORCE_DARK_AUTO:
+                    menu.findItem(R.id.menu_force_dark_auto).setChecked(true);
+                    break;
+                case WebSettings.FORCE_DARK_ON:
+                    menu.findItem(R.id.menu_force_dark_on).setChecked(true);
+                    break;
+            }
+        }
         return true;
     }
 
@@ -567,6 +586,18 @@ public class WebViewBrowserActivity extends AppCompatActivity {
                     }
                 }
                 return true;
+            case R.id.menu_force_dark_off:
+                mWebView.getSettings().setForceDark(WebSettings.FORCE_DARK_OFF);
+                item.setChecked(true);
+                return true;
+            case R.id.menu_force_dark_auto:
+                mWebView.getSettings().setForceDark(WebSettings.FORCE_DARK_AUTO);
+                item.setChecked(true);
+                return true;
+            case R.id.menu_force_dark_on:
+                mWebView.getSettings().setForceDark(WebSettings.FORCE_DARK_ON);
+                item.setChecked(true);
+                return true;
             case R.id.start_animation_activity:
                 startActivity(new Intent(this, WebViewAnimationTestActivity.class));
                 return true;