Suppress embedding fonts when the skp's fonts match the OS fonts.

The million SKPs generated require >5T of storage. A good deal
of that are copies of system fonts.

Chrome built with
#DEFINE SK_WHITELIST_SERIALIZED_TYPEFACES
will omit the font data if the font matches a precomputed
checksum.

The captured SKP prepends sk_ to the names of fonts that
have their data omitted. The SKP consumer can either add
renamed fonts from the recording machine, or add

gDeserializeTypefaceDelegate = WhitelistDeserializeTypeface;

which strips the sk_ prefix when deserializing typefaces.

whitelist_typefaces --check
Computes the checksums of fallback
fonts and returns 0 if the checksums match the checked-in
file SkWhitelistChecksum.cpp.

whitelist_typefaces --generate
Writes an updated version of SkWhitelistChecksum.cpp.

(Added Mike since this modifies a public header)

R=bungeman@google.com,rmistry@google.com,reed@google.com

Review URL: https://codereview.chromium.org/1317913005
9 files changed