Make the dependency of enable_print_preview and enable_pdf explicit

build/config/BUILD.gn

Index: build/config/BUILD.gn
diff --git a/build/config/BUILD.gn b/build/config/BUILD.gn
index 0ca8e18a5bb1ecef7d74ecac665bcab4a6d07a69..cc2ffb3c6ee815a4003c0dbc94ab225fadba122a 100644
--- a/build/config/BUILD.gn
+++ b/build/config/BUILD.gn
@@ -82,6 +82,12 @@ config("feature_flags") {
       # Can be defined without ENABLE_BASIC_PRINTING.
       defines += [ "ENABLE_PRINT_PREVIEW=1" ]
     }
+    if ((enable_basic_printing && is_win) || enable_print_preview) {
+      # Windows basic printing or print preview requires pdf enabled.
+      assert(enable_pdf,
+             "Windows basic printing or print preview needs pdf: " +
+                 "set enable_pdf=true.")
+    }
   }
   if (enable_spellcheck) {
     defines += [ "ENABLE_SPELLCHECK=1" ]