Fixed compiler warning C4267 'conversion from 'size_t' to 'type', possible loss of data'

BUG=angleproject:1120

Change-Id: I01ef10bea7f487c2b394d030c76628f38d2ea645
Reviewed-on: https://chromium-review.googlesource.com/292780
Tested-by: Cooper Partin <coopp@microsoft.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libANGLE/renderer/gl/VertexArrayGL.cpp b/src/libANGLE/renderer/gl/VertexArrayGL.cpp
index a2ca881..13c9539 100644
--- a/src/libANGLE/renderer/gl/VertexArrayGL.cpp
+++ b/src/libANGLE/renderer/gl/VertexArrayGL.cpp
@@ -384,9 +384,10 @@
                 // Compute where the 0-index vertex would be.
                 const size_t vertexStartOffset = curBufferOffset - (indexRange.start * destStride);
 
-                mFunctions->vertexAttribPointer(idx, attrib.size, attrib.type,
-                                                attrib.normalized, destStride,
-                                                reinterpret_cast<const GLvoid*>(vertexStartOffset));
+                mFunctions->vertexAttribPointer(
+                    idx, attrib.size, attrib.type, attrib.normalized,
+                    static_cast<GLsizei>(destStride),
+                    reinterpret_cast<const GLvoid *>(vertexStartOffset));
 
                 curBufferOffset += destStride * streamedVertexCount;