Extract some logic from transport_dib into shared_memory.

ui/surface/transport_dib_posix.cc

 // Copyright (c) 2012 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 "ui/surface/transport_dib.h"
 
 #include <sys/stat.h>
 #include <unistd.h>
 
 #include "base/logging.h"
@@ skipping 33 matching lines @@
   return dib.release();
 }
 
 // static
 TransportDIB* TransportDIB::CreateWithHandle(Handle handle) {
   return new TransportDIB(handle);
 }
 
 // static
 bool TransportDIB::is_valid_handle(Handle dib) {
-  return dib.fd >= 0;
+  return base::SharedMemory::IsHandleValid(dib);
 }
 
 // static
 bool TransportDIB::is_valid_id(Id id) {
 #if defined(OS_ANDROID)
   return is_valid_handle(id);
 #else
   return id != 0;
 #endif
 }
 
 skia::PlatformCanvas* TransportDIB::GetPlatformCanvas(int w, int h) {
   if ((!memory() && !Map()) || !VerifyCanvasSize(w, h))
     return NULL;
-  return skia::CreatePlatformCanvas(w, h, true, 
+  return skia::CreatePlatformCanvas(w, h, true,
                                     reinterpret_cast<uint8_t*>(memory()),
                                     skia::RETURN_NULL_ON_FAILURE);
 }
 
 bool TransportDIB::Map() {
   if (!is_valid_handle(handle()))
     return false;
 #if defined(OS_ANDROID)
   if (!shared_memory_.Map(0))
     return false;
   size_ = shared_memory_.mapped_size();
 #else
   if (memory())
     return true;
 
-  struct stat st;
-  if ((fstat(shared_memory_.handle().fd, &st) != 0) ||
-      (!shared_memory_.Map(st.st_size))) {
+  int size = base::SharedMemory::GetSizeFromSharedMemoryHandle(
+      shared_memory_.handle());
+  if (size == -1 || (!shared_memory_.Map(size)))

[Nico, 2015/05/30 00:02:43]

nit: no parens around (!...) on the rhs (yes, they were there before, but they
didn't belong there before either)

[erikchen, 2015/05/30 00:10:50]

Done. The new version is indeed easier to read.

     return false;
-  }
 
-  size_ = st.st_size;
+  size_ = size;
 #endif
   return true;
 }
 
 void* TransportDIB::memory() const {
   return shared_memory_.memory();
 }
 
 TransportDIB::Id TransportDIB::id() const {
 #if defined(OS_ANDROID)
   return handle();
 #else
   return shared_memory_.id();
 #endif
 }
 
 TransportDIB::Handle TransportDIB::handle() const {
   return shared_memory_.handle();
 }