Add the "is_ensemble" build variable.

media/base/BUILD.gn

Index: media/base/BUILD.gn
diff --git a/media/base/BUILD.gn b/media/base/BUILD.gn
index fd1bfe0263cfc94e608cf2ae831bb415fecf1c99..e43653a2c2becfeab65a31629117a06ccd743da3 100644
--- a/media/base/BUILD.gn
+++ b/media/base/BUILD.gn
@@ -217,7 +217,7 @@ source_set("base") {
     sources += [ "media_posix.cc" ]
   }
 
-  if (is_linux && use_x11) {
+  if (is_linux && use_x11 && !is_ensemble) {
     configs += [
       "//build/config/linux:x11",
       "//build/config/linux:xext",
@@ -254,6 +254,10 @@ source_set("base") {
       "keyboard_event_counter.h",
     ]
   }
+
+  if (is_ensemble) {
+    deps -= [ "//skia" ]
+  }
 }
 
 # Minimal media component for media/cast on iOS.