Remove a bunch of TOOLKIT_GTK in content/ and gpu/, as well as NPAPI plugins on linux

content/public/test/mock_render_process_host.cc

Index: content/public/test/mock_render_process_host.cc
diff --git a/content/public/test/mock_render_process_host.cc b/content/public/test/mock_render_process_host.cc
index 8576af8e229f09a136da5506948f2461c19e0b69..b07f5e50e14e076723cd1dbe86ab8dd8f3876c3d 100644
--- a/content/public/test/mock_render_process_host.cc
+++ b/content/public/test/mock_render_process_host.cc
@@ -151,8 +151,6 @@ TransportDIB* MockRenderProcessHost::MapTransportDIB(TransportDIB::Id dib_id) {
                        &duped, 0, TRUE, DUPLICATE_SAME_ACCESS))
     duped = NULL;
   return TransportDIB::Map(duped);
-#elif defined(TOOLKIT_GTK)
-  return TransportDIB::Map(dib_id.shmkey);
 #elif defined(OS_ANDROID)
   // On Android, Handles and Ids are the same underlying type.
   return TransportDIB::Map(dib_id);