exp/html: simplify some of the parser's internal methods.
exp/html: simplify some of the parser's internal methods.

benchmark          old ns/op    new ns/op    delta
BenchmarkParser      4006888      3950604   -1.40%

R=r, andybalholm
CC=golang-dev
http://codereview.appspot.com/6301070

scirelli/scirelli-go,webfd/go-zh,d0f/go-zh,Triskite/willstone-goclone,webfd/go-zh,rdp/rogerpack2005-golang,scirelli/scirelli-go,sanjosh/sanjos100-tipc,rflanagan/reginaldflanagan-project1,Triskite/willstone-goclone,sanjosh/sanjos100-tipc,mhennings/marcohennings-go,Triskite/willstone-goclone,mhennings/marcohennings-go,bryanxu/go-zh,mhennings/marcohennings-go,d0f/go-zh,webfd/go-zh,d0f/go-zh,rdp/rogerpack2005-golang,scirelli/scirelli-go,bryanxu/go-zh,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,mhennings/marcohennings-go,rdp/rogerpack2005-golang,rflanagan/reginaldflanagan-project1,Triskite/willstone-goclone,rflanagan/reginaldflanagan-project1,bryanxu/go-zh,glycerine/jeaten-go-arrayof-structof,rflanagan/reginaldflanagan-project1,webfd/go-zh,webfd/go-zh,mhennings/marcohennings-go,Triskite/willstone-goclone,glycerine/jeaten-go-arrayof-structof,rflanagan/reginaldflanagan-project1,mhennings/marcohennings-go,Triskite/willstone-goclone,bryanxu/go-zh,glycerine/jeaten-go-arrayof-structof,webfd/go-zh,scirelli/scirelli-go,mhennings/marcohennings-go,sanjosh/sanjos100-tipc,scirelli/scirelli-go,d0f/go-zh,mhennings/marcohennings-go,d0f/go-zh,bryanxu/go-zh,sanjosh/sanjos100-tipc,rflanagan/reginaldflanagan-project1,glycerine/jeaten-go-arrayof-structof,glycerine/jeaten-go-arrayof-structof,rflanagan/reginaldflanagan-project1,rdp/rogerpack2005-golang,sanjosh/sanjos100-tipc,bryanxu/go-zh,d0f/go-zh,webfd/go-zh,glycerine/jeaten-go-arrayof-structof,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,sanjosh/sanjos100-tipc,rdp/rogerpack2005-golang,d0f/go-zh,scirelli/scirelli-go,scirelli/scirelli-go,webfd/go-zh,scirelli/scirelli-go,Triskite/willstone-goclone,bryanxu/go-zh,Triskite/willstone-goclone,rdp/rogerpack2005-golang,rflanagan/reginaldflanagan-project1,bryanxu/go-zh,d0f/go-zh