Optionally clear PlatformCanvas instances.

ui/gfx/surface/transport_dib_linux.cc

 // Copyright (c) 2011 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/gfx/surface/transport_dib.h"
 
 #include <errno.h>
 #include <stdlib.h>
 #include <sys/ipc.h>
 #include <sys/shm.h>
@@ skipping 76 matching lines @@
 
 // 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())))
+  if (!canvas->initialize(
+          w, h,
+          skia::PlatformDevice::FLAGS_OPAQUE |
+              skia::PlatformDevice::FLAGS_INITIALIZED,

[Jeff Timanus, 2012/02/23 22:14:10]

The canvas can be explicitly cleared in the various flavours of TransportDIB,
based on the platform.

+          reinterpret_cast<uint8_t*>(memory())))
     return NULL;
   return canvas.release();
 }
 
 bool TransportDIB::Map() {
   if (!is_valid_id(key_))
     return false;
   if (address_ != kInvalidAddress)
     return true;
 
@@ skipping 24 matching lines @@
 }
 
 XID TransportDIB::MapToX(Display* display) {
   if (!x_shm_) {
     x_shm_ = ui::AttachSharedMemory(display, key_.shmkey);
     display_ = display;
   }
 
   return x_shm_;
 }