Convert SetVisuallyDeemphasized IPC to mojo

extensions/renderer/BUILD.gn

Index: extensions/renderer/BUILD.gn
diff --git a/extensions/renderer/BUILD.gn b/extensions/renderer/BUILD.gn
index 8c98927a3133143a55cfd77e701de29d3a1bb392..67e8baed490ea49754b1ac483d4715c5e4f5a674 100644
--- a/extensions/renderer/BUILD.gn
+++ b/extensions/renderer/BUILD.gn
@@ -4,6 +4,7 @@
 
 import("//build/config/features.gni")
 import("//extensions/features/features.gni")
+import("//mojo/public/tools/bindings/mojom.gni")
 
 assert(enable_extensions)
 
@@ -233,6 +234,7 @@ source_set("renderer") {
     "//content:resources",
     "//extensions:extensions_resources",
     "//extensions/common/api",
+    "//extensions/renderer:mojo",
     "//gin",
     "//mojo/edk/js",
     "//mojo/public/js",
@@ -278,6 +280,12 @@ source_set("renderer") {
   }
 }
 
+mojom("mojo") {
+  sources = [
+    "mojo/frame_observer.mojom",
+  ]
+}
+
 source_set("unit_tests") {
   testonly = true
   sources = [