BUILD.gn: skia_enable_pdf

BUG=skia:

Change-Id: Icf616bec73e81aad97815b519566ff5b9db611e3
Reviewed-on: https://skia-review.googlesource.com/6495
Commit-Queue: Hal Canary <halcanary@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>
diff --git a/BUILD.gn b/BUILD.gn
index 24651c7..c4158c6 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -28,6 +28,7 @@
   skia_enable_android_framework_defines = false
   skia_enable_discrete_gpu = true
   skia_enable_gpu = true
+  skia_enable_pdf = true
   skia_enable_tools = is_skia_standalone
   skia_enable_vulkan_debug_layers = is_skia_standalone && is_debug
   skia_vulkan_sdk = getenv("VULKAN_SDK")
@@ -429,7 +430,8 @@
 }
 
 optional("pdf") {
-  enabled = skia_use_zlib
+  enabled = skia_use_zlib && skia_enable_pdf
+  public_defines = [ "SK_SUPPORT_PDF" ]
 
   deps = [
     "//third_party/zlib",
@@ -439,7 +441,7 @@
 
   if (skia_use_sfntly) {
     deps += [ "//third_party/sfntly" ]
-    public_defines = [ "SK_PDF_USE_SFNTLY" ]
+    public_defines += [ "SK_PDF_USE_SFNTLY" ]
   }
 }