Adds a TransportDIB::Id value that is explicitly invalid and use it when compositing

app/surface/transport_dib_linux.cc

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <errno.h>
 #include <stdlib.h>
 #include <sys/ipc.h>
 #include <sys/shm.h>
 
 #include "app/surface/transport_dib.h"
 #include "base/logging.h"
 #include "base/scoped_ptr.h"
 #include "skia/ext/platform_canvas.h"
 #include "ui/base/x/x11_util.h"
 #include "ui/gfx/size.h"
 
 // The shmat system call uses this as it's invalid return address
 static void *const kInvalidAddress = (void*) -1;
 
 TransportDIB::TransportDIB()
-    : key_(-1),
-      address_(kInvalidAddress),
+    : address_(kInvalidAddress),
       x_shm_(0),
       display_(NULL),
       size_(0) {
 }
 
 TransportDIB::~TransportDIB() {
   if (address_ != kInvalidAddress) {
     shmdt(address_);
     address_ = kInvalidAddress;
   }
@@ skipping 19 matching lines @@
   void* address = shmat(shmkey, NULL /* desired address */, 0 /* flags */);
   // Here we mark the shared memory for deletion. Since we attached it in the
   // line above, it doesn't actually get deleted but, if we crash, this means
   // that the kernel will automatically clean it up for us.
   shmctl(shmkey, IPC_RMID, 0);
   if (address == kInvalidAddress)
     return NULL;
 
   TransportDIB* dib = new TransportDIB;
 
-  dib->key_ = shmkey;
+  dib->key_.shmkey = shmkey;
   dib->address_ = address;
   dib->size_ = size;
   return dib;
 }
 
 // static
 TransportDIB* TransportDIB::Map(Handle handle) {
   scoped_ptr<TransportDIB> dib(CreateWithHandle(handle));
   if (!dib->Map())
     return NULL;
   return dib.release();
 }
 
 // static
 TransportDIB* TransportDIB::CreateWithHandle(Handle shmkey) {
   TransportDIB* dib = new TransportDIB;
-  dib->key_ = shmkey;
+  dib->key_.shmkey = shmkey;
   return dib;
 }
 
 // static
-bool TransportDIB::is_valid(Handle dib) {
+bool TransportDIB::is_valid_handle(Handle dib) {
   return dib >= 0;
 }
 
+// static
+bool TransportDIB::is_valid_id(Id id) {
+  return id.shmkey != -1;
+}
+
 skia::PlatformCanvas* TransportDIB::GetPlatformCanvas(int w, int h) {
   if (address_ == kInvalidAddress && !Map())
     return NULL;
   scoped_ptr<skia::PlatformCanvas> canvas(new skia::PlatformCanvas);
   if (!canvas->initialize(w, h, true, reinterpret_cast<uint8_t*>(memory())))
     return NULL;
   return canvas.release();
 }
 
 bool TransportDIB::Map() {
-  if (!is_valid(key_))
+  if (!is_valid_id(key_))
     return false;
   if (address_ != kInvalidAddress)
     return true;
 
   struct shmid_ds shmst;
-  if (shmctl(key_, IPC_STAT, &shmst) == -1)
+  if (shmctl(key_.shmkey, IPC_STAT, &shmst) == -1)
     return false;
 
-  void* address = shmat(key_, NULL /* desired address */, 0 /* flags */);
+  void* address = shmat(key_.shmkey, NULL /* desired address */, 0 /* flags */);
   if (address == kInvalidAddress)
     return false;
 
   address_ = address;
   size_ = shmst.shm_segsz;
   return true;
 }
 
 void* TransportDIB::memory() const {
   DCHECK_NE(address_, kInvalidAddress);
   return address_;
 }
 
 TransportDIB::Id TransportDIB::id() const {
   return key_;
 }
 
 TransportDIB::Handle TransportDIB::handle() const {
-  return key_;
+  return key_.shmkey;
 }
 
 XID TransportDIB::MapToX(Display* display) {
   if (!x_shm_) {
-    x_shm_ = ui::AttachSharedMemory(display, key_);
+    x_shm_ = ui::AttachSharedMemory(display, key_.shmkey);
     display_ = display;
   }
 
   return x_shm_;
 }