Hook up the blink platform GN file.

Hooks up the blink GN build to the main GN build. Android is currently disabled
(some dependencies are not complete yet).

R=eseidel@chromium.org, thakis@chromium.org

Review URL: https://codereview.chromium.org/296513002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@271707 0039d316-1c4b-4281-b951-d872f2087c98

BUILD.gn

@@ -38,7 +38,6 @@ group("root") {
     "//net",
     #"//sdch",
     "//skia",
-    #"//third_party/WebKit/Source/platform",
     "//third_party/brotli",
     "//third_party/iccjpeg",
     "//third_party/icu",
@@ -53,6 +52,7 @@ group("root") {
     "//third_party/smhasher:cityhash",
     "//third_party/smhasher:murmurhash3",
     "//third_party/smhasher:pmurhash",
+    "//third_party/WebKit/Source/platform",
     "//third_party/WebKit/Source/wtf",
     "//third_party/zlib",
     "//third_party:jpeg",
@@ -79,6 +79,7 @@ group("root") {
       "//gpu/command_buffer/client",  # Needs Skia.
       "//net",
       "//third_party/libusb",
+      "//third_party/WebKit/Source/platform",
       "//third_party/WebKit/Source/wtf",  # TODO(brettw) re-enable for Android.
       "//tools/gn",
       "//ui/base:ui_base",