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

components/view_manager/public/interfaces/quads.mojom

Index: components/view_manager/public/interfaces/quads.mojom
diff --git a/components/view_manager/public/interfaces/quads.mojom b/components/view_manager/public/interfaces/quads.mojom
index 221d27f2bf07408138535ff77ce9ceb48146776e..b3af3d5949f741a50a2965bd7499bf1e2a3aec16 100644
--- a/components/view_manager/public/interfaces/quads.mojom
+++ b/components/view_manager/public/interfaces/quads.mojom
@@ -20,7 +20,7 @@ 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 {