Add cc::SurfaceInfo::is_valid()

cc/ipc/surface_info_struct_traits.h

 // Copyright 2017 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.
 
 #ifndef CC_IPC_SURFACE_INFO_STRUCT_TRAITS_H_
 #define CC_IPC_SURFACE_INFO_STRUCT_TRAITS_H_
 
 #include "cc/ipc/surface_info.mojom-shared.h"
 #include "cc/surfaces/surface_info.h"
 
 namespace mojo {
 
 template <>
 struct StructTraits<cc::mojom::SurfaceInfoDataView, cc::SurfaceInfo> {
   static const cc::SurfaceId& surface_id(const cc::SurfaceInfo& surface_info) {
     return surface_info.id();
   }
 
   static float device_scale_factor(const cc::SurfaceInfo& surface_info) {
     return surface_info.device_scale_factor();
   }
 
   static const gfx::Size& size_in_pixels(const cc::SurfaceInfo& surface_info) {
     return surface_info.size_in_pixels();
   }
 
   static bool Read(cc::mojom::SurfaceInfoDataView data, cc::SurfaceInfo* out) {
     out->device_scale_factor_ = data.device_scale_factor();
     return data.ReadSurfaceId(&out->id_) &&
-           data.ReadSizeInPixels(&out->size_in_pixels_);
+           data.ReadSizeInPixels(&out->size_in_pixels_) && out->is_valid();

[Fady Samuel, 2017/02/28 02:54:32]

I'm not sure if compilers are guaranteed to process these conditions in order.

Do this:

out->device_scale_factor_ = data.device_scale_factor();
if (!data.ReadSurfaceId(&out->id_))
  return false;

if (!data.ReadSizeInPixels(&out->size_in_pixels_))
  return false;

return out->is_valid();

[Tom Sepez, 2017/02/28 17:52:01]

This is fine; sequence points in C occur at the end of the evaluation of the
right operand of a && expression.

   }
 };
 
 }  // namespace mojo
 
 #endif  // CC_IPC_SURFACE_INFO_STRUCT_TRAITS_H_