Individually enable and disable SkCodecs

cmake/CMakeLists.txt

 # Boilerplate.
 cmake_minimum_required (VERSION 3.1)   # First version with CMAKE_CXX_STANDARD.
 project (skimake)
 set (CMAKE_CXX_STANDARD 11)
 
 # Default to Release mode.  We're mainly targeting Skia users, not Skia developers.
 if (NOT CMAKE_BUILD_TYPE)
     set (CMAKE_BUILD_TYPE Release)
 endif ()
 
@@ skipping 127 matching lines @@
 if (UNIX AND NOT APPLE)
     find_package (Freetype)
     # Same deal for fontconfig.
     find_path (FONTCONFIG_INCLUDE_DIRS "fontconfig/fontconfig.h")
     find_library (FONTCONFIG_LIBRARIES fontconfig)
     find_package (GIF)
     find_package (JPEG)
     find_package (PNG)
 endif()
 
-# Decide whether to turn on SkCodec.
-# TODO (skbug.com/4956): We should be able to turn specific codecs on and off rather than
-#                        disabling all of them if one library is missing.
-if (NOT (GIF_FOUND AND JPEG_FOUND AND PNG_FOUND AND WEBP_INCLUDE_DIRS AND WEBP_LIBRARIES))
-    remove_srcs(../src/codec/* ../src/android/*)
-endif()
-
 # Do not compile SkRawCodec.
 remove_srcs(../src/codec/*Raw*.cpp)
 
 # TODO: macro away this if (found) ... else() ... endif() stuff.
 
 if (EXPAT_FOUND)
     list (APPEND private_includes ${EXPAT_INCLUDE_DIRS})
     list (APPEND libs             ${EXPAT_LIBRARIES})
 else()
     remove_srcs (../src/ports/SkFontMgr_android_parser.cpp)
 endif()
 
 if (GIF_FOUND)
     list (APPEND private_includes ${GIF_INCLUDE_DIRS})
     list (APPEND libs             ${GIF_LIBRARIES})
+    add_definitions(-DSK_CODEC_DECODES_GIF)
 else()
     remove_srcs(../src/images/*gif*)
+    remove_srcs(../src/codec/*Gif*)
 endif()
 
 if (JPEG_FOUND)
     list (APPEND private_includes ${JPEG_INCLUDE_DIRS})
     list (APPEND libs             ${JPEG_LIBRARIES})
+    add_definitions(-DSK_CODEC_DECODES_JPEG)
 else()
     remove_srcs(../src/images/*jpeg*)
+    remove_srcs(../src/images/*Jpeg*)
+    remove_srcs(../src/codec/*Jpeg*)
 endif()
 
 if (LUA_FOUND)
     list (APPEND private_includes ${LUA_INCLUDE_DIR})
     list (APPEND libs             ${LUA_LIBRARIES})
 else()
     remove_srcs(../src/utils/*Lua*)
 endif()
 
 if (PNG_FOUND)
     list (APPEND private_includes ${PNG_INCLUDE_DIRS})
     list (APPEND libs             ${PNG_LIBRARIES})
     add_definitions(-DPNG_SKIP_SETJMP_CHECK)
     add_definitions(-DPNG_SKIP_SKIA_OPTS)
+    add_definitions(-DSK_CODEC_DECODES_PNG)
 else()
     remove_srcs(../src/images/*png*)
+    remove_srcs(../src/images/*ico*)
+    remove_srcs(../src/codec/*Png*)
+    remove_srcs(../src/codec/*Ico*)
 endif()
 
 if (ZLIB_FOUND)
     list (APPEND private_includes ${ZLIB_INCLUDE_DIRS})
     list (APPEND libs             ${ZLIB_LIBRARIES})
     remove_srcs(../src/doc/SkDocument_PDF_None.cpp)
 else()
     remove_srcs(../src/pdf/*.cpp ../src/doc/SkDocument_PDF.cpp)
 endif()
 
 if (WEBP_INCLUDE_DIRS AND WEBP_LIBRARIES)
     list (APPEND private_includes ${WEBP_INCLUDE_DIRS})
     list (APPEND libs             ${WEBP_LIBRARIES})
+    add_definitions(-DSK_CODEC_DECODES_WEBP)
 else()
     remove_srcs(../src/images/*webp*)
+    remove_srcs(../src/codec/*Webp*)
 endif()
 
 if (FREETYPE_FOUND)
     list (APPEND private_includes ${FREETYPE_INCLUDE_DIRS})
     list (APPEND libs             ${FREETYPE_LIBRARIES})
 endif()
 
 if (FONTCONFIG_INCLUDE_DIRS AND FONTCONFIG_LIBRARIES)
     list (APPEND private_includes ${FONTCONFIG_INCLUDE_DIRS})
     list (APPEND libs             ${FONTCONFIG_LIBRARIES})
@@ skipping 97 matching lines @@
         file (APPEND ${skia_h_path} "#include \"${filename_component}\"\n")
       endif ()
     endforeach()
   endif()
 endforeach()
 file(APPEND ${skia_h_path} "\n#endif  // skia_DEFINED\n")
 
 # Now build a simple example app that uses Skia via libskia.so.
 add_executable(example example.cpp)
 target_link_libraries(example skia ${OPENGL_LIBRARIES})