Fix warnings from size_t conversions.

src/libANGLE/renderer/d3d/VertexBuffer.cpp

@@ -92,7 +92,7 @@ gl::Error VertexBufferInterface::setBufferSize(unsigned int size)
 gl::ErrorOrResult<unsigned int> VertexBufferInterface::getSpaceRequired(
     const gl::VertexAttribute &attrib,
     const gl::VertexBinding &binding,
-    GLsizei count,
+    size_t count,
     GLsizei instances) const
 {
     unsigned int spaceRequired = 0;

src/libANGLE/renderer/d3d/VertexBuffer.h

@@ -93,7 +93,7 @@ class VertexBufferInterface : angle::NonCopyable
 
     gl::ErrorOrResult<unsigned int> getSpaceRequired(const gl::VertexAttribute &attrib,
                                                      const gl::VertexBinding &binding,
-                                                     GLsizei count,
+                                                     size_t count,
                                                      GLsizei instances) const;
     BufferFactoryD3D *const mFactory;
     VertexBuffer *mVertexBuffer;

src/libANGLE/renderer/d3d/d3d11/Renderer11.cpp

@@ -3583,7 +3583,8 @@ gl::ErrorOrResult<unsigned int> Renderer11::getVertexSpaceRequired(
     const unsigned int divisor = binding.getDivisor();
     if (instances == 0 || divisor == 0)
     {
-        elementCount = count;
+        // This could be a clipped cast.
+        elementCount = gl::clampCast<unsigned int>(count);
     }
     else
     {