Adds a ParseTrailers method to SpdyUtils, with some basic validation of the header keys provided.

net/quic/spdy_utils.h

Index: net/quic/spdy_utils.h
diff --git a/net/quic/spdy_utils.h b/net/quic/spdy_utils.h
index 87fa0087a77964faabc8dae1230e7f047b2712a2..76b667dd6716bdc9b527f8da17127428c5fc8aea 100644
--- a/net/quic/spdy_utils.h
+++ b/net/quic/spdy_utils.h
@@ -29,6 +29,16 @@ class NET_EXPORT_PRIVATE SpdyUtils {
                            int* content_length,
                            SpdyHeaderBlock* headers);
 
+  // Parses |data| as a std::string containing serialized HTTP/2 HEADERS frame,
+  // populating |trailers| with the key->value std:pairs found.
+  // The :final-offset header will be excluded from |trailers|, and instead the
+  // value will be copied to |final_byte_offset|.
+  // Returns true on success, false if parsing fails, or invalid keys are found.
+  static bool ParseTrailers(const char* data,
+                            uint32 data_len,
+                            size_t* final_byte_offset,
+                            SpdyHeaderBlock* trailers);
+
  private:
   DISALLOW_COPY_AND_ASSIGN(SpdyUtils);
 };