Bug 1045561 Use a WebIDL Func attribute to conditionally enable Fetch Headers. r=ehsan r=bz

dom/fetch/Headers.cpp

@@ -8,6 +8,8 @@
 
 #include "mozilla/ErrorResult.h"
 #include "mozilla/dom/UnionTypes.h"
+#include "mozilla/dom/WorkerPrivate.h"
+#include "mozilla/Preferences.h"
 
 #include "nsCharSeparatedTokenizer.h"
 #include "nsContentUtils.h"
@@ -28,6 +30,32 @@ NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(Headers)
   NS_INTERFACE_MAP_ENTRY(nsISupports)
 NS_INTERFACE_MAP_END
 
+// static
+bool
+Headers::PrefEnabled(JSContext* aCx, JSObject* aObj)
+{
+  using mozilla::dom::workers::WorkerPrivate;
+  using mozilla::dom::workers::GetWorkerPrivateFromContext;
+
+  if (NS_IsMainThread()) {
+    static bool sPrefCacheInit = false;
+    static bool sPrefEnabled = false;
+    if (sPrefCacheInit) {
+      return sPrefEnabled;
+    }
+    Preferences::AddBoolVarCache(&sPrefEnabled, "dom.fetch.enabled");
+    sPrefCacheInit = true;
+    return sPrefEnabled;
+  }
+
+  WorkerPrivate* workerPrivate = GetWorkerPrivateFromContext(aCx);
+  if (!workerPrivate) {
+    return false;
+  }
+
+  return workerPrivate->DOMFetchEnabled();
+}
+
 // static
 already_AddRefed<Headers>
 Headers::Constructor(const GlobalObject& aGlobal,

dom/fetch/Headers.h

@@ -54,6 +54,8 @@ public:
     SetIsDOMBinding();
   }
 
+  static bool PrefEnabled(JSContext* cx, JSObject* obj);
+
   static already_AddRefed<Headers>
   Constructor(const GlobalObject& aGlobal,
               const Optional<HeadersOrByteStringSequenceSequenceOrByteStringMozMap>& aInit,

dom/fetch/moz.build

@@ -12,6 +12,10 @@ UNIFIED_SOURCES += [
     'Headers.cpp',
 ]
 
+LOCAL_INCLUDES += [
+    '../workers',
+]
+
 FAIL_ON_WARNINGS = True
 MSVC_ENABLE_PGO = True
 FINAL_LIBRARY = 'xul'

dom/webidl/Headers.webidl

@@ -20,7 +20,7 @@ enum HeadersGuardEnum {
 
 [Constructor(optional HeadersInit init),
  // FIXME: Exposed=Window,Worker,
- Pref="dom.fetch.enabled"]
+ Func="mozilla::dom::Headers::PrefEnabled"]
 interface Headers {
   [Throws] void append(ByteString name, ByteString value);
   [Throws] void delete(ByteString name);

dom/workers/RegisterBindings.cpp

@@ -64,6 +64,8 @@ WorkerPrivate::RegisterBindings(JSContext* aCx, JS::Handle<JSObject*> aGlobal)
       !DOMExceptionBinding::GetConstructorObject(aCx, aGlobal) ||
       !EventBinding::GetConstructorObject(aCx, aGlobal) ||
       !FileReaderSyncBinding_workers::GetConstructorObject(aCx, aGlobal) ||
+      (HeadersBinding::ConstructorEnabled(aCx, aGlobal) &&
+       !HeadersBinding::GetConstructorObject(aCx, aGlobal)) ||
       !ImageDataBinding::GetConstructorObject(aCx, aGlobal) ||
       !MessageEventBinding::GetConstructorObject(aCx, aGlobal) ||
       !MessagePortBinding::GetConstructorObject(aCx, aGlobal) ||
@@ -80,12 +82,6 @@ WorkerPrivate::RegisterBindings(JSContext* aCx, JS::Handle<JSObject*> aGlobal)
     return false;
   }
 
-  if (DOMFetchEnabled()) {
-    if (!HeadersBinding::GetConstructorObject(aCx, aGlobal)) {
-      return false;
-    }
-  }
-
   if (!JS_DefineProfilingFunctions(aCx, aGlobal)) {
     return false;
   }