Individually enable and disable SkCodecs

gyp/codec.gyp

Index: gyp/codec.gyp
diff --git a/gyp/codec.gyp b/gyp/codec.gyp
index 9537f8aa51c3406f9f41f98a35283646a6e28918..e9bec29dae54640c3aeeb882aed94600437f763b 100644
--- a/gyp/codec.gyp
+++ b/gyp/codec.gyp
@@ -22,11 +22,6 @@
         'libpng.gyp:libpng',
         'libwebp.gyp:libwebp',
       ],
-      'cflags':[
-        # FIXME: This gets around a longjmp warning. See

[scroggo, 2016/02/17 14:55:55]

Did this get fixed in this patch? Or maybe it was fixed before and we didn't
notice?

Unfortunately that link is no longer valid, but I guess we should see it quickly
on the compile bot if we still need it.

[msarett, 2016/02/17 15:13:47]

I *think* this was fixed before and we didn't notice.  Sorry for the unrelated
change.

-        # http://build.chromium.org/p/client.skia.compile/builders/Build-Ubuntu-GCC-x86_64-Release-Trybot/builds/113/steps/build%20most/logs/stdio
-        '-Wno-clobbered -Wno-error',
-      ],
       'include_dirs': [
         '../include/codec',
         '../include/private',
@@ -65,6 +60,15 @@
         ],
       },
       'defines': [
+        # Allow the client to turn on/off individual codecs.  This can be useful

[scroggo, 2016/02/17 14:55:55]

Is the idea that a client would modify this file if they want to disable one? We
could add gyp variables that would decide whether to turn them on, like we do
for RAW, but if no one needs that, I'm fine to leave as is.

[mtklein, 2016/02/17 14:59:30]

Let's not add switches no one's asking to flip yet.

[msarett, 2016/02/17 15:13:47]

Let's leave as is for now - if we find we need switches later, we can add them.

I'm guessing (maybe I'm wrong) that clients who use this build system generally
have all the dependencies that we need.  This feature is probably more useful
for CMake/Google3 clients etc.  Maybe the comment is misleading?

[scroggo, 2016/02/17 15:20:00]

Yes :)

[msarett, 2016/02/17 15:26:28]

Improved this comment.

+        # when some of the dependencies are not present.
+        'SK_CODEC_DECODES_GIF',
+        'SK_CODEC_DECODES_JPEG',
+        'SK_CODEC_DECODES_PNG',
+        'SK_CODEC_DECODES_WEBP',
+
+        # Turn on optimizations when the appropriate version of libjpeg-turbo is
+        # present.      
         'TURBO_HAS_SKIP',
         'TURBO_HAS_565',
       ],