gfx: Use unsigned strides for gpu memory buffers.

services/ui/public/interfaces/gpu_memory_buffer.mojom

Index: services/ui/public/interfaces/gpu_memory_buffer.mojom
diff --git a/services/ui/public/interfaces/gpu_memory_buffer.mojom b/services/ui/public/interfaces/gpu_memory_buffer.mojom
index c4685113b8d365bfd689c561315680f83e06e886..160d3bea6bc444562e1ae81779c28dc00308dcb7 100644
--- a/services/ui/public/interfaces/gpu_memory_buffer.mojom
+++ b/services/ui/public/interfaces/gpu_memory_buffer.mojom
@@ -11,7 +11,7 @@ struct NativePixmapHandle {
   handle fd;
 
   // The stride used when accessing the buffer via a memory mapping.
-  int32 stride;
+  uint32 stride;
 };
 
 
@@ -20,7 +20,7 @@ struct GpuMemoryBufferHandle {
   gfx.mojom.GpuMemoryBufferId id;
   handle buffer_handle;
   uint32 offset;
-  int32 stride;
+  uint32 stride;
   NativePixmapHandle? native_pixmap_handle;
   // TODO(fsamuel): Add support for Machports.
 };