Clear IOSurfaces immediately after creating them.

ui/gfx/mac/io_surface.cc

 // Copyright 2015 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/mac/io_surface.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "base/logging.h"
@@ skipping 130 matching lines @@
   AddIntegerValue(properties, kIOSurfaceWidth, size.width());
   AddIntegerValue(properties, kIOSurfaceHeight, size.height());
   AddIntegerValue(properties, kIOSurfacePixelFormat, PixelFormat(format));
   if (num_planes > 1) {
     CFDictionaryAddValue(properties, kIOSurfacePlaneInfo, planes);
   } else {
     AddIntegerValue(properties, kIOSurfaceBytesPerElement,
                     BytesPerElement(format, 0));
   }
 
-  return IOSurfaceCreate(properties);
+  IOSurfaceRef surface = IOSurfaceCreate(properties);
+
+  // Zero-initialize the texture.
+  // https://code.google.com/p/chromium/issues/detail?id=584760#c17

[reveman, 2016/02/17 18:37:37]

This bug cannot be accessed outside google. Can we include an explanation here
instead of just referring to the bug? 

[erikchen, 2016/02/17 18:51:15]

Done.

+  IOReturn r = IOSurfaceLock(surface, kIOSurfaceLockAvoidSync, NULL);

[reveman, 2016/02/17 18:37:37]

I feel like I might have asked this before so sorry if I'm repeating myself.

Can we just do this here instead:

IOReturn r = IOSurfaceLock(surface, 0, nullptr);
DCHECK_EQ(r, kIOReturnSuccess);
IOSurfaceUnlock(surface, 0, nullptr);

I'd prefer to keep this as simple as possible and avoid shipping code that is
not tested by the unit test you added.

[erikchen, 2016/02/17 18:51:15]

Done.

+  DCHECK(r == kIOReturnSuccess || r == kIOReturnCannotLock);
+  if (r == kIOReturnSuccess) {
+    IOSurfaceUnlock(surface, kIOSurfaceLockAvoidSync, NULL);

[reveman, 2016/02/17 18:37:37]

nit: nullptr here and above

[erikchen, 2016/02/17 18:51:15]

Done.

+  } else {
+    r = IOSurfaceLock(surface, 0, nullptr);
+    DCHECK_EQ(kIOReturnSuccess, r);
+    r = IOSurfaceUnlock(surface, 0, nullptr);
+    DCHECK_EQ(kIOReturnSuccess, r);
+  }
+
+  return surface;
 }
 
 }  // namespace gfx