POSIX: Rewrite IPC's interaction with FileDescriptor

The FileDescriptor API is clearly too hard to use. It's the only IPC
data type which is non-POD and serialising an invalid file descriptor
is fatal to Chrome on POSIX. The use of Maybe is possibly non-obvious
to non-functional programmers.

This patch merges Maybe and FileDescriptor so that serialising invalid
file descriptors is permitted and results in -1 at the other end.
(Serialising /closed/ a file descriptor is still fatal.) Also, it adds
a pointer in base/file_descriptor.h to instructions for its use with
IPC. Although it's generally bad practice to mention IPC in base, in
this case I cannot find another suitable location.

Review URL: http://codereview.chromium.org/39208


git-svn-id: svn://svn.chromium.org/chrome/trunk/src@11041 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 8 insertions, 10 deletions

diff --git a/chrome/browser/renderer_host/render_widget_helper.cc b/chrome/browser/renderer_host/render_widget_helper.cc
index 715a85b..24e1710 100644
--- a/chrome/browser/renderer_host/render_widget_helper.cc
+++ b/chrome/browser/renderer_host/render_widget_helper.cc
@@ -263,21 +263,21 @@ TransportDIB* RenderWidgetHelper::MapTransportDIB(TransportDIB::Id dib_id) {
 }
 
 void RenderWidgetHelper::AllocTransportDIB(
-    size_t size, IPC::Maybe<TransportDIB::Handle>* result) {
+    size_t size, TransportDIB::Handle* result) {
   base::SharedMemory* shared_memory = new base::SharedMemory();
   if (!shared_memory->Create(L"", false /* read write */,
                              false /* do not open existing */, size)) {
-    result->valid = false;
+    result->fd = -1;
+    result->auto_close = false;
     delete shared_memory;
     return;
   }
 
-  result->valid = true;
-  shared_memory->GiveToProcess(0 /* pid, not needed */, &result->value);
+  shared_memory->GiveToProcess(0 /* pid, not needed */, result);
 
   // Keep a copy of the file descriptor around
   AutoLock locked(allocated_dibs_lock_);
-  allocated_dibs_[shared_memory->id()] = dup(result->value.fd);
+  allocated_dibs_[shared_memory->id()] = dup(result->fd);
 }
 
 void RenderWidgetHelper::FreeTransportDIB(TransportDIB::Id dib_id) {
diff --git a/chrome/browser/renderer_host/render_widget_helper.h b/chrome/browser/renderer_host/render_widget_helper.h
index eb13ff0..317a72e 100644
--- a/chrome/browser/renderer_host/render_widget_helper.h
+++ b/chrome/browser/renderer_host/render_widget_helper.h
@@ -11,7 +11,6 @@
 #include "base/ref_counted.h"
 #include "base/lock.h"
 #include "base/waitable_event.h"
-#include "chrome/common/ipc_maybe.h"
 #include "chrome/common/modal_dialog_event.h"
 #include "chrome/common/transport_dib.h"
 
@@ -131,7 +130,7 @@ class RenderWidgetHelper :
 
 #if defined(OS_MACOSX)
   // Called on the IO thread to handle the allocation of a transport DIB
-  void AllocTransportDIB(size_t size, IPC::Maybe<TransportDIB::Handle>* result);
+  void AllocTransportDIB(size_t size, TransportDIB::Handle* result);
 
   // Called on the IO thread to handle the freeing of a transport DIB
   void FreeTransportDIB(TransportDIB::Id dib_id);
diff --git a/chrome/browser/renderer_host/resource_message_filter.cc b/chrome/browser/renderer_host/resource_message_filter.cc
index 1f78df1..4460c37 100644
--- a/chrome/browser/renderer_host/resource_message_filter.cc
+++ b/chrome/browser/renderer_host/resource_message_filter.cc
@@ -870,7 +870,7 @@ void ResourceMessageFilter::OnSetAudioVolume(
 
 #if defined(OS_MACOSX)
 void ResourceMessageFilter::OnAllocTransportDIB(
-    size_t size, IPC::Maybe<TransportDIB::Handle>* handle) {
+    size_t size, TransportDIB::Handle* handle) {
   render_widget_helper_->AllocTransportDIB(size, handle);
 }
 
diff --git a/chrome/browser/renderer_host/resource_message_filter.h b/chrome/browser/renderer_host/resource_message_filter.h
index 679a0ac..823685a 100644
--- a/chrome/browser/renderer_host/resource_message_filter.h
+++ b/chrome/browser/renderer_host/resource_message_filter.h
@@ -19,7 +19,6 @@
 #include "chrome/browser/net/resolve_proxy_msg_helper.h"
 #include "chrome/browser/renderer_host/resource_dispatcher_host.h"
 #include "chrome/common/ipc_channel_proxy.h"
-#include "chrome/common/ipc_maybe.h"
 #include "chrome/common/modal_dialog_event.h"
 #include "chrome/common/notification_observer.h"
 #include "chrome/common/transport_dib.h"
@@ -215,7 +214,7 @@ class ResourceMessageFilter : public IPC::ChannelProxy::MessageFilter,
 
   // Browser side transport DIB allocation
   void OnAllocTransportDIB(size_t size,
-                           IPC::Maybe<TransportDIB::Handle>* result);
+                           TransportDIB::Handle* result);
   void OnFreeTransportDIB(TransportDIB::Id dib_id);
 
   // We have our own clipboard service because we want to access the clipboard