Reland: cc: Fix size_t to int truncations in layers/ output/ playback/ quads/

components/view_manager/public/interfaces/quads.mojom

 // Copyright 2014 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.
 
 module mojo;
 
 import "components/view_manager/public/interfaces/surface_id.mojom";
 import "ui/mojo/geometry/geometry.mojom";
 
 struct Color {
   uint32 rgba;
 };
 
 // TODO(jamesr): Populate subtype fields.
 struct CheckerboardQuadState {};
 
 struct DebugBorderQuadState {};
 
 struct IoSurfaceContentQuadState {};
 
 struct RenderPassId {
   int32 layer_id;
-  int32 index;
+  uint32 index;

[sky, 2015/06/08 14:53:13]

Seems wrong to have this and RenderPassId::index difference types. Should this
be uint64 to match the RenderPassId::index? Or should  RenderPassId::index be
uint32_t to match this?

[vmpstr, 2015/06/08 18:59:27]

The problem is that I think the correct type for RenderPassId::index is size_t,
since it's an index into a vector. For mojo, I was following a similar
situation:
https://code.google.com/p/chromium/codesearch#chromium/src/mojo/converters/su...
(a dcheck and a static_cast from size_t to uint32_t). 

Making this uint64 would probably cause more truncation issues when used as an
index on systems where size_t is 4 bytes...

Do you know if there are any plans to support size_t in mojom files? That would
probably be the best solution if we want the types to match perfectly.

 };
 
 struct RenderPassQuadState {
   RenderPassId render_pass_id;
 
   // If nonzero, resource id of mask to use when drawing this pass.
   uint32 mask_resource_id;
   PointF mask_uv_scale;
   Size mask_texture_size;
 
@@ skipping 169 matching lines @@
 
 struct Pass {
   RenderPassId id;
   Rect output_rect;
   Rect damage_rect;
   Transform transform_to_root_target;
   bool has_transparent_background;
   array<Quad> quads;
   array<SharedQuadState> shared_quad_states;
 };