Add SkCodec, including PNG implementation.

gyp/codec.gyp

+# GYP file for codec project.
+{
+  'targets': [
+    {
+      'target_name': 'codec',
+      'product_name': 'skia_codec',
+      'type': 'static_library',
+      'standalone_static_library': 1,
+      'dependencies': [
+        'core.gyp:*',
+        'libjpeg.gyp:*',
+        'etc1.gyp:libetc1',
+        'ktx.gyp:libSkKTX',
+        'libwebp.gyp:libwebp',
+        'utils.gyp:utils',
+      ],
+      'include_dirs': [
+        '../include/codec',
+        '../src/codec',
+      ],
+      'sources': [
+        '../src/codec/SkCodec.cpp',
+        '../src/codec/SkCodec_libpng.cpp',
+        '../src/codec/SkSwizzler.cpp',
+      ],
+      'conditions': [
+        [ 'skia_os in ["linux", "freebsd", "openbsd", "solaris"]', {
+          'export_dependent_settings': [

[djsollen, 2015/02/25 16:02:19]

why do we want to expose these settings further up the stack?

[scroggo, 2015/02/25 18:00:54]

This copies images.gyp almost exactly. Not sure what our reasoning was there.

I removed it though. If it causes any problems we should find out in testing.

+            'libpng.gyp:libpng',
+            'giflib.gyp:giflib'
+          ],
+          'dependencies': [
+            'libpng.gyp:libpng',
+            'giflib.gyp:giflib'
+          ],
+          # end libpng/libgif stuff
+        }],
+        # FIXME: NaCl should be just like linux, etc, above, but it currently is separated out
+        # to remove gif. Once gif is supported by naclports, this can be merged into the above
+        # condition.
+        [ 'skia_os == "nacl"', {
+          'sources!': [
+            '../src/images/SkImageDecoder_libgif.cpp',
+            '../src/images/SkMovie_gif.cpp',
+          ],
+        }],
+        [ 'skia_os == "android"', {
+          'dependencies': [
+             'android_deps.gyp:gif',
+             'android_deps.gyp:png',

[djsollen, 2015/02/25 16:02:19]

for android we should link in the most recent copy of libpng not the one that
SkImageDecoder uses.

[scroggo, 2015/02/25 18:00:54]

Done.

[scroggo, 2015/02/26 17:45:36]

I neglected to pay attention to the fact that libpng.gyp, when not building with
skia_libpng_static, makes Android pull in android_deps, which in turn pulls in
dependencies, which builds a different static library - the one with the Android
mods. Latest patch set fixes this for real - we now set skia_libpng_static on
Android, so it statically builds the right version of libpng.

Derek, is that the right thing to do? Will there be any problems with codec (a
static library) including one static libpng and images (another static library)
including a different static libpng?

+          ],
+          'conditions': [
+            [ 'skia_android_framework == 0', {
+              'export_dependent_settings': [
+                'android_deps.gyp:png',
+                'libjpeg.gyp:*'
+              ],
+            }],
+          ],
+        }],
+        [ 'skia_os == "chromeos"', {
+          'dependencies': [
+             'chromeos_deps.gyp:gif',
+             'libpng.gyp:libpng',
+          ],
+        }],
+        [ 'skia_os == "ios"', {
+           'include_dirs': [
+             '../include/utils/mac',
+           ],
+        }],
+      ],
+      'direct_dependent_settings': {
+        'include_dirs': [
+          '../include/codec',
+        ],
+      },
+    },
+  ],
+}