Fix "value possibly truncated" warnings on MSVC, net/spdy/ edition.

net/spdy/hpack_huffman_table.h

Index: net/spdy/hpack_huffman_table.h
diff --git a/net/spdy/hpack_huffman_table.h b/net/spdy/hpack_huffman_table.h
index f776ddd2887e63dccabd9e026a5f54b36cbc5a53..55352d4e639c14b8d7054c3603a3c5ddaf987c15 100644
--- a/net/spdy/hpack_huffman_table.h
+++ b/net/spdy/hpack_huffman_table.h
@@ -67,7 +67,8 @@ class NET_EXPORT_PRIVATE HpackHuffmanTable {
   // Prepares HpackHuffmanTable to encode & decode the canonical Huffman
   // code as determined by the given symbols. Must be called exactly once.
   // Returns false if the input symbols define an invalid coding, and true
-  // otherwise. Symbols must be presented in ascending ID order with no gaps.
+  // otherwise. Symbols must be presented in ascending ID order with no gaps,
+  // and |symbol_count| must fit in a uint16.
   bool Initialize(const Symbol* input_symbols, size_t symbol_count);
 
   // Returns whether Initialize() has been successfully called.