pilot for the codec link-forcing system

Pilot for the codec link-forcing system

This patch shows how I propose to implement the link forcing mechanism for the codecs. I have added declare & define macros in SkImageDecoder.h and SkImageEncoder.h. A declare line will be added for each codec in SkImageDecoder.h and/or SkImageEncoder.h. A define line will be added to each codec (e.g., SkImageDecoder_libjpeg.cpp). Finally each module that uses a codec (e.g., cmykjpeg.cpp) will need a forcing method that invokes the codec creation function.

[robertphillips, 2012-03-23 12:47:13]

http://codereview.appspot.com/5881055/diff/1/src/images/SkImageDecoder_libjpe...
File src/images/SkImageDecoder_libjpeg.cpp (right):

http://codereview.appspot.com/5881055/diff/1/src/images/SkImageDecoder_libjpe...
src/images/SkImageDecoder_libjpeg.cpp:663: static const unsigned char gHeader[]
= { 0xFF, 0xD8, 0xFF };
This change silences a compiler warning on Windows (i.e., "warning C4309:
'initializing' : truncation of constant value").

[reed1, 2012-03-23 13:31:55]

Can we add some explanatory comments above each macro in the public headers?

I guess there no way to share those, and/or place them in a common .h? Its a
little funny that they are there (4 new macros), but I don't see any client code
using them (other than in the header itself.

[robertphillips, 2012-03-23 14:10:23]

I have added comments to the header files and propagated the necessary changes
to all the other codecs.

[robertphillips, 2012-03-23 18:14:55]

committed as r3481