[aw-dark] Add API that allows an app to specify how dark mode should be respected.

 - Media query only
 - Force dark unless page supports dark mode via meta tag and media query
 - Always force dark (disable media query).

Bug: 1001516
Change-Id: Ida620311e8b4811f6fddffbeaf9d7f40b427493e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1798349Reviewed-by: Tobias Sargeant <tobiasjs@chromium.org>
Commit-Queue: Anna Malova <amalova@chromium.org>
Cr-Commit-Position: refs/heads/master@{#695633}

android_webview/browser/aw_settings.cc

@@ -496,30 +496,53 @@ void AwSettings::PopulateWebPreferencesLocked(JNIEnv* env,
   web_prefs->scroll_top_left_interop_enabled =
       Java_AwSettings_getScrollTopLeftInteropEnabledLocked(env, obj);
 
+  bool is_dark_mode;
   switch (Java_AwSettings_getForceDarkModeLocked(env, obj)) {
     case ForceDarkMode::FORCE_DARK_OFF:
-      web_prefs->force_dark_mode_enabled = false;
+      is_dark_mode = false;
       break;
     case ForceDarkMode::FORCE_DARK_ON:
-      web_prefs->force_dark_mode_enabled = true;
+      is_dark_mode = true;
       break;
     case ForceDarkMode::FORCE_DARK_AUTO: {
       AwContents* contents = AwContents::FromWebContents(web_contents());
-      web_prefs->force_dark_mode_enabled =
-          contents && contents->GetViewTreeForceDarkState();
+      is_dark_mode = contents && contents->GetViewTreeForceDarkState();
       break;
     }
   }
-
-  // Blink's behavior is that if the preferred color scheme matches the
-  // supported color scheme, then force dark will be disabled, otherwise
-  // the preferred color scheme will be reset to no preference. Therefore
-  // when enabling force dark, we also set the preferred color scheme to
-  // dark so that dark themed content will be preferred over force darkening.
   web_prefs->preferred_color_scheme =
-      web_prefs->force_dark_mode_enabled
-          ? blink::PreferredColorScheme::kDark
-          : blink::PreferredColorScheme::kNoPreference;
+      is_dark_mode ? blink::PreferredColorScheme::kDark
+                   : blink::PreferredColorScheme::kNoPreference;
+  if (is_dark_mode) {
+    switch (Java_AwSettings_getDarkModePreferencesLocked(env, obj)) {
+      case DarkModePreferences::FORCE_DARK_ONLY: {
+        web_prefs->preferred_color_scheme =
+            blink::PreferredColorScheme::kNoPreference;
+        web_prefs->force_dark_mode_enabled = true;
+        break;
+      }
+      case DarkModePreferences::MEDIA_QUERY_ONLY: {
+        web_prefs->preferred_color_scheme = blink::PreferredColorScheme::kDark;
+        web_prefs->force_dark_mode_enabled = false;
+        break;
+      }
+      // Blink's behavior is that if the preferred color scheme matches the
+      // supported color scheme, then force dark will be disabled, otherwise
+      // the preferred color scheme will be reset to no preference. Therefore
+      // when enabling force dark, we also set the preferred color scheme to
+      // dark so that dark themed content will be preferred over force
+      // darkening.
+      case DarkModePreferences::PREFER_MEDIA_QUERY_OVER_FORCE_DARK: {
+        web_prefs->preferred_color_scheme = blink::PreferredColorScheme::kDark;
+        web_prefs->force_dark_mode_enabled = true;
+        break;
+      }
+    }
+  } else {
+    web_prefs->preferred_color_scheme =
+        blink::PreferredColorScheme::kNoPreference;
+    web_prefs->force_dark_mode_enabled = false;
+  }
 }
 
 bool AwSettings::GetAllowFileAccess() {

android_webview/browser/aw_settings.h

@@ -28,6 +28,13 @@ class AwSettings : public content::WebContentsObserver {
     FORCE_DARK_ON = 2,
   };
 
+  // GENERATED_JAVA_ENUM_PACKAGE: org.chromium.android_webview.settings
+  enum DarkModePreferences {
+    FORCE_DARK_ONLY = 0,
+    MEDIA_QUERY_ONLY = 1,
+    PREFER_MEDIA_QUERY_OVER_FORCE_DARK = 2,
+  };
+
   static AwSettings* FromWebContents(content::WebContents* web_contents);
   static bool GetAllowSniffingFileUrls();
 

android_webview/java/src/org/chromium/android_webview/AwSettings.java

@@ -16,6 +16,7 @@ import android.support.annotation.IntDef;
 import android.util.Log;
 import android.webkit.WebSettings;
 
+import org.chromium.android_webview.settings.DarkModePreferences;
 import org.chromium.android_webview.settings.ForceDarkMode;
 import org.chromium.base.ContextUtils;
 import org.chromium.base.ThreadUtils;
@@ -62,6 +63,15 @@ public class AwSettings {
     @ForceDarkMode
     private int mForceDarkMode = ForceDarkMode.FORCE_DARK_AUTO;
 
+    public static final int FORCE_DARK_ONLY = DarkModePreferences.FORCE_DARK_ONLY;
+    public static final int MEDIA_QUERY_ONLY = DarkModePreferences.MEDIA_QUERY_ONLY;
+    // This option requires RuntimeEnabledFeatures::MetaColorSchemeEnabled()
+    public static final int PREFER_MEDIA_QUERY_OVER_FORCE_DARK =
+            DarkModePreferences.PREFER_MEDIA_QUERY_OVER_FORCE_DARK;
+
+    @DarkModePreferences
+    private int mDarkModePreferences = DarkModePreferences.PREFER_MEDIA_QUERY_OVER_FORCE_DARK;
+
     // This class must be created on the UI thread. Afterwards, it can be
     // used from any thread. Internally, the class uses a message queue
     // to call native code on the UI thread only.
@@ -1712,6 +1722,29 @@ public class AwSettings {
         }
     }
 
+    @DarkModePreferences
+    public int getDarkModePreferences() {
+        synchronized (mAwSettingsLock) {
+            return getDarkModePreferencesLocked();
+        }
+    }
+
+    @CalledByNative
+    @DarkModePreferences
+    public int getDarkModePreferencesLocked() {
+        assert Thread.holdsLock(mAwSettingsLock);
+        return mDarkModePreferences;
+    }
+
+    public void setDarkModePreferences(@DarkModePreferences int darkModePreferences) {
+        synchronized (mAwSettingsLock) {
+            if (mDarkModePreferences != darkModePreferences) {
+                mDarkModePreferences = darkModePreferences;
+                mEventHandler.updateWebkitPreferencesLocked();
+            }
+        }
+    }
+
     @CalledByNative
     private boolean getAllowRunningInsecureContentLocked() {
         assert Thread.holdsLock(mAwSettingsLock);