gfx: Use unsigned strides for gpu memory buffers.

ui/gfx/gpu_memory_buffer.h

Index: ui/gfx/gpu_memory_buffer.h
diff --git a/ui/gfx/gpu_memory_buffer.h b/ui/gfx/gpu_memory_buffer.h
index df5d7b54c2ffb14eaf2854ad45fd94e27ea42e6e..966413d11f3c90903577516f89a4a8b6ad479a69 100644
--- a/ui/gfx/gpu_memory_buffer.h
+++ b/ui/gfx/gpu_memory_buffer.h
@@ -48,7 +48,7 @@ struct GFX_EXPORT GpuMemoryBufferHandle {
   GpuMemoryBufferId id;
   base::SharedMemoryHandle handle;
   uint32_t offset;
-  int32_t stride;
+  uint32_t stride;
 #if defined(USE_OZONE)
   NativePixmapHandle native_pixmap_handle;
 #elif defined(OS_MACOSX) && !defined(OS_IOS)
@@ -89,7 +89,7 @@ class GFX_EXPORT GpuMemoryBuffer {
 
   // Fills the stride in bytes for each plane of the buffer. The stride of
   // plane K is stored at index K-1 of the |stride| array.
-  virtual int stride(size_t plane) const = 0;
+  virtual uint32_t stride(size_t plane) const = 0;
 
   // Set the color space in which this buffer should be interpreted when used
   // for scanout. Note that this will not impact texturing from the buffer.