GYP changes and scripts for compiling Skia for ChromeOS

DEPS

 use_relative_paths = True
 
 # Dependencies on outside packages, as needed for developers/bots that use
 # "gclient" instead of raw SVN access.
 #
 # For now, this must be maintained in parallel with "SVN externals"
 # dependencies for developers who use raw SVN instead of "gclient".
 # See third_party/externals/README
 #
 deps = {
   # DEPS using https://chromium.googlesource.com are pulled from chromium @ r205199
   # (see https://chromium.googlesource.com/chromium/chromium/+/c59bfa8ef877f45bfa859669053859857af1d279)
   "third_party/externals/angle" : "https://chromium.googlesource.com/external/angleproject.git@36cced4a9b48cc1e654fbb27477f12fb77b63c91",
   "third_party/externals/freetype" : "https://android.googlesource.com/platform/external/freetype.git@android-4.2.2_r1.2",
   "third_party/externals/gyp" : "https://chromium.googlesource.com/external/gyp.git@8f42386eafcd7ddf1947cab2808a76c315ff30cc",
   "third_party/externals/libjpeg" : "https://chromium.googlesource.com/chromium/deps/libjpeg_turbo.git@82ce8a6d4ebe12a177c0c3597192f2b4f09e81c3",
   "third_party/externals/jsoncpp" : "https://chromium.googlesource.com/external/jsoncpp/jsoncpp.git@ab1e40f3bce061ea6f9bdc60351d6cde2a4f872b",
   "third_party/externals/jsoncpp-chromium" : "https://chromium.googlesource.com/chromium/src/third_party/jsoncpp.git@41239939c0c60481f34887d52c038facf05f5533",
   "third_party/externals/libwebp" : "https://chromium.googlesource.com/webm/libwebp.git@0.3.0",
   "third_party/externals/podofo" : "https://skia.googlesource.com/third_party/podofo.git@skia_ext",
 }
 
 deps_os = {
   "android": {
     "platform_tools/android/third_party/externals/expat" : "https://android.googlesource.com/platform/external/expat.git@android-4.2.2_r1.2",
     "platform_tools/android/third_party/externals/gif" : "https://android.googlesource.com/platform/external/giflib.git@android-4.2.2_r1.2",
     "platform_tools/android/third_party/externals/png" : "https://android.googlesource.com/platform/external/libpng.git@android-4.2.2_r1.2",
     "platform_tools/android/third_party/externals/jpeg" : "https://android.googlesource.com/platform/external/jpeg.git@android-4.2.2_r1.2",
   },
+  "chromeos": {
+    "platform_tools/chromeos/third_party/externals/gif" : "https://android.googlesource.com/platform/external/giflib.git@android-4.2.2_r1.2",
+  },
 }
 
 #hooks = [
 #  {
 #    # A change to a .gyp, .gypi, or to GYP itself should run the generator.
 #    "pattern": ".",
 #    "action": ["python", "trunk/gyp_skia"],
 #  },
 #]