Fix force-dark-mode not working on first time page loading.

For few url schemes, the light color scheme is forced as they don't
have dark mode theme yet. This was done by calling
UpdatePreferredColorSchemesBasedOnURLIfNeeded(). This function gets
called from OverrideWebkitPrefs() and
OverrideWebPreferencesAfterNavigation(). The prior function sets the
prefs preferred color scheme based on IsNightModeEnabled() for Android
or native theme scheme for other platforms, but the later function
does not set it. This patch now sets preferred color scheme for all
platforms at one place in UpdatePreferredColorScheme().

As --force-dark-mode switch works only for preferred color scheme,
until dark scheme is detected in page, default background is white
which causes flicker once dark content is rendered. However this is
a separate issue.

Bug: 1137213
Change-Id: I5567149a5644a6d3d30ceabd65fb1f25e1971ad4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2494296Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Prashant Nevase <prashant.n@samsung.com>
Cr-Commit-Position: refs/heads/master@{#822741}

chrome/browser/chrome_content_browser_client.cc

@@ -2919,6 +2919,68 @@ std::unique_ptr<net::ClientCertIdentity> AutoSelectCertificate(
   return nullptr;
 }
 
+#if !defined(OS_ANDROID)
+blink::mojom::PreferredColorScheme ToBlinkPreferredColorScheme(
+    ui::NativeTheme::PreferredColorScheme native_theme_scheme) {
+  switch (native_theme_scheme) {
+    case ui::NativeTheme::PreferredColorScheme::kDark:
+      return blink::mojom::PreferredColorScheme::kDark;
+    case ui::NativeTheme::PreferredColorScheme::kLight:
+      return blink::mojom::PreferredColorScheme::kLight;
+  }
+
+  NOTREACHED();
+}
+#endif  // !defined(OS_ANDROID)
+
+// Returns true if preferred color scheme is modified based on at least one of
+// the following -
+// |url| - Last committed url.
+// |web_contents| - For Android based on IsNightModeEnabled().
+// |native_theme| - For other platforms based on native theme scheme.
+bool UpdatePreferredColorScheme(WebPreferences* web_prefs,
+                                const GURL& url,
+                                WebContents* web_contents,
+                                const ui::NativeTheme* native_theme) {
+  auto old_preferred_color_scheme = web_prefs->preferred_color_scheme;
+
+#if defined(OS_ANDROID)
+  auto* delegate = TabAndroid::FromWebContents(web_contents)
+                       ? static_cast<android::TabWebContentsDelegateAndroid*>(
+                             web_contents->GetDelegate())
+                       : nullptr;
+  if (delegate) {
+    web_prefs->preferred_color_scheme =
+        delegate->IsNightModeEnabled()
+            ? blink::mojom::PreferredColorScheme::kDark
+            : blink::mojom::PreferredColorScheme::kLight;
+  }
+#else
+  // Update based on native theme scheme.
+  web_prefs->preferred_color_scheme =
+      ToBlinkPreferredColorScheme(native_theme->GetPreferredColorScheme());
+#endif  // defined(OS_ANDROID)
+
+  // Force a light preferred color scheme on certain URLs if kWebUIDarkMode is
+  // disabled; some of the UI is not yet correctly themed.
+  if (!base::FeatureList::IsEnabled(features::kWebUIDarkMode)) {
+    // Update based on last committed url.
+    bool force_light = url.SchemeIs(content::kChromeUIScheme);
+#if BUILDFLAG(ENABLE_EXTENSIONS)
+    if (!force_light) {
+      force_light = url.SchemeIs(extensions::kExtensionScheme) &&
+                    url.host_piece() == extension_misc::kPdfExtensionId;
+    }
+#endif
+    if (force_light) {
+      web_prefs->preferred_color_scheme =
+          blink::mojom::PreferredColorScheme::kLight;
+    }
+  }
+
+  return old_preferred_color_scheme != web_prefs->preferred_color_scheme;
+}
+
 }  // namespace
 
 base::OnceClosure ChromeContentBrowserClient::SelectClientCertificate(
@@ -3135,26 +3197,6 @@ content::TtsPlatform* ChromeContentBrowserClient::GetTtsPlatform() {
 #endif
 }
 
-bool UpdatePreferredColorSchemesBasedOnURLIfNeeded(WebPreferences* web_prefs,
-                                                   const GURL& url) {
-  // Force a light preferred color scheme on certain URLs if kWebUIDarkMode is
-  // disabled; some of the UI is not yet correctly themed.
-  if (base::FeatureList::IsEnabled(features::kWebUIDarkMode))
-    return false;
-  bool force_light = url.SchemeIs(content::kChromeUIScheme);
-#if BUILDFLAG(ENABLE_EXTENSIONS)
-  if (!force_light) {
-    force_light = url.SchemeIs(extensions::kExtensionScheme) &&
-                  url.host_piece() == extension_misc::kPdfExtensionId;
-  }
-#endif
-  auto old_preferred_color_scheme = web_prefs->preferred_color_scheme;
-  if (force_light)
-    web_prefs->preferred_color_scheme =
-        blink::mojom::PreferredColorScheme::kLight;
-  return old_preferred_color_scheme != web_prefs->preferred_color_scheme;
-}
-
 void ChromeContentBrowserClient::OverrideWebkitPrefs(
     RenderViewHost* rvh,
     WebPreferences* web_prefs) {
@@ -3302,11 +3344,6 @@ void ChromeContentBrowserClient::OverrideWebkitPrefs(
 
       web_prefs->picture_in_picture_enabled =
           delegate->IsPictureInPictureEnabled();
-
-      web_prefs->preferred_color_scheme =
-          delegate->IsNightModeEnabled()
-              ? blink::mojom::PreferredColorScheme::kDark
-              : blink::mojom::PreferredColorScheme::kLight;
     }
 #endif  // defined(OS_ANDROID)
 
@@ -3424,7 +3461,6 @@ void ChromeContentBrowserClient::OverrideWebkitPrefs(
     }
   }
 
-  auto* native_theme = GetWebTheme();
 #if !defined(OS_ANDROID)
   if (IsAutoplayAllowedByPolicy(contents, prefs)) {
     // If autoplay is allowed by policy then force the no user gesture required
@@ -3443,20 +3479,9 @@ void ChromeContentBrowserClient::OverrideWebkitPrefs(
             ? blink::mojom::AutoplayPolicy::kDocumentUserActivationRequired
             : blink::mojom::AutoplayPolicy::kNoUserGestureRequired;
   }
-
-  switch (native_theme->GetPreferredColorScheme()) {
-    case ui::NativeTheme::PreferredColorScheme::kDark:
-      web_prefs->preferred_color_scheme =
-          blink::mojom::PreferredColorScheme::kDark;
-      break;
-    case ui::NativeTheme::PreferredColorScheme::kLight:
-      web_prefs->preferred_color_scheme =
-          blink::mojom::PreferredColorScheme::kLight;
-      break;
-  }
 #endif  // !defined(OS_ANDROID)
 
-  switch (native_theme->GetPreferredContrast()) {
+  switch (GetWebTheme()->GetPreferredContrast()) {
     case ui::NativeTheme::PreferredContrast::kNoPreference:
       web_prefs->preferred_contrast =
           blink::mojom::PreferredContrast::kNoPreference;
@@ -3469,8 +3494,8 @@ void ChromeContentBrowserClient::OverrideWebkitPrefs(
       break;
   }
 
-  UpdatePreferredColorSchemesBasedOnURLIfNeeded(
-      web_prefs, rvh->GetSiteInstance()->GetSiteURL());
+  UpdatePreferredColorScheme(web_prefs, rvh->GetSiteInstance()->GetSiteURL(),
+                             contents, GetWebTheme());
 
   web_prefs->translate_service_available = TranslateService::IsAvailable(prefs);
 
@@ -3496,8 +3521,8 @@ void ChromeContentBrowserClient::OverrideWebkitPrefs(
 bool ChromeContentBrowserClient::OverrideWebPreferencesAfterNavigation(
     WebContents* web_contents,
     WebPreferences* prefs) {
-  return UpdatePreferredColorSchemesBasedOnURLIfNeeded(
-      prefs, web_contents->GetLastCommittedURL());
+  return UpdatePreferredColorScheme(prefs, web_contents->GetLastCommittedURL(),
+                                    web_contents, GetWebTheme());
 }
 
 void ChromeContentBrowserClient::BrowserURLHandlerCreated(