Patch by Artur Wyszynski with some changes by myself:

* Resolved TODO: The type of the gradient is no longer encoded twice in the
  app_server link protocoll.
* Moved instantiation of the BGradient into the LinkReceiver::ReadGradient()
  method.
* Check success for (at least) ReadGradient() in ServerWindow.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@28150 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/private/app/LinkReceiver.h

@@ -13,9 +13,10 @@
 
 #include <OS.h>
 
+
+class BGradient;
 class BString;
 class BRegion;
-class BGradient;
 
 
 namespace BPrivate {
@@ -38,7 +39,7 @@ class LinkReceiver {
 		status_t ReadString(BString& string, size_t* _length = NULL);
 		status_t ReadString(char* buffer, size_t bufferSize);
 		status_t ReadRegion(BRegion* region);
-		status_t ReadGradient(BGradient *gradient);
+		status_t ReadGradient(BGradient** gradient);
 
 		template <class Type> status_t Read(Type *data)
 			{ return Read(data, sizeof(Type)); }

headers/private/app/ServerLink.h

@@ -66,7 +66,7 @@ class ServerLink {
 		status_t ReadString(char** _string, size_t* _length = NULL);
 		status_t ReadRegion(BRegion *region);
 		status_t ReadShape(BShape *shape);
-		status_t ReadGradient(BGradient *gradient);
+		status_t ReadGradient(BGradient **gradient);
 		template <class Type> status_t Read(Type *data);
 
 		// convenience methods