Bug 1372072 - Part 1: Spoofing network information API and blocking ontypechange event when 'privacy.resistFingerprinting' is true. r=arthuredelstein,baku

This patch makes the network information API always returns the default type 'unknown'
and blocking the ontypechange event while connection type changed when 'privacy.
resistFingerprinting' is true.

MozReview-Commit-ID: 4eOdHgAGtyY

--HG--
extra : rebase_source : 172f6dd01b45761f441a8ac81fd82e5caa7c68f6
extra : source : 41a89cb123e1b50f28f062f071196e85d92cfb10

dom/network/Connection.cpp

@@ -100,7 +100,8 @@ Connection::Update(ConnectionType aType, bool aIsWifi, bool aDHCPGateway,
   mIsWifi = aIsWifi;
   mDHCPGateway = aDHCPGateway;
 
-  if (aNotify && previousType != aType) {
+  if (aNotify && previousType != aType &&
+      !nsContentUtils::ShouldResistFingerprinting()) {
     DispatchTrustedEvent(CHANGE_EVENT_NAME);
   }
 }

dom/network/Connection.h

@@ -9,6 +9,7 @@
 
 #include "mozilla/DOMEventTargetHelper.h"
 #include "mozilla/dom/NetworkInformationBinding.h"
+#include "nsContentUtils.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsINetworkProperties.h"
 
@@ -52,7 +53,11 @@ public:
   virtual JSObject* WrapObject(JSContext* aCx,
                                JS::Handle<JSObject*> aGivenProto) override;
 
-  ConnectionType Type() const { return mType; }
+  ConnectionType Type() const
+  {
+    return nsContentUtils::ShouldResistFingerprinting() ?
+             static_cast<ConnectionType>(ConnectionType::Unknown) : mType;
+  }
 
   IMPL_EVENT_HANDLER(typechange)