Update system colors dynamically

This change exposes LayoutTheme::PlatformColorsDidChange() through
WebRenderTheme. This allows system colors to update dynamically when
new colors are sent from the browser process.

Bug: 970285
Change-Id: Ic3b75dfec668dc5523b0e12765574e66dd35ff8f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1797057Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Commit-Queue: Kurt Catti-Schmidt <kschmi@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#700308}

content/renderer/render_thread_impl.cc

@@ -150,6 +150,7 @@
 #include "third_party/blink/public/web/blink.h"
 #include "third_party/blink/public/web/web_document.h"
 #include "third_party/blink/public/web/web_frame.h"
+#include "third_party/blink/public/web/web_render_theme.h"
 #include "third_party/blink/public/web/web_script_controller.h"
 #include "third_party/blink/public/web/web_security_policy.h"
 #include "third_party/blink/public/web/web_view.h"
@@ -2160,6 +2161,7 @@ void RenderThreadImpl::UpdateSystemColorInfo(
   ui::NativeTheme::GetInstanceForWeb()->UpdateSystemColorInfo(
       params->is_dark_mode, params->is_high_contrast,
       params->preferred_color_scheme, params->colors);
+  blink::SystemColorsChanged();
 }
 
 void RenderThreadImpl::PurgePluginListCache(bool reload_pages) {

third_party/blink/public/web/web_render_theme.h

@@ -47,6 +47,8 @@ BLINK_EXPORT void SetSelectionColors(unsigned active_background_color,
                                      unsigned inactive_background_color,
                                      unsigned inactive_foreground_color);
 
+BLINK_EXPORT void SystemColorsChanged();
+
 }  // namespace blink
 
 #endif

third_party/blink/renderer/core/exported/web_render_theme.cc

@@ -53,4 +53,8 @@ void SetSelectionColors(unsigned active_background_color,
       inactive_background_color, inactive_foreground_color);
 }
 
+void SystemColorsChanged() {
+  LayoutTheme::GetTheme().PlatformColorsDidChange();
+}
+
 }  // namespace blink