DEPS: Sync Git subtree mirrors instead of symlinking into chromium/src

tools-webrtc/autoroller/unittests/testdata/DEPS

 # DEPS file for unit tests.
 
 vars = {
   'chromium_git': 'https://chromium.googlesource.com',
   'chromium_revision': '1b9c098a08e40114e44b6c1ec33ddf95c40b901d',
 }
 
 deps = {
   # Entry that is a directory in Chromium, so we're using a Git subtree mirror for it.
   'src/build':
     Var('chromium_git') + '/chromium/src/build' + '@' + '52f7afeca991d96d68cf0507e20dbdd5b845691f',
 
   # Entry that's also a DEPS entry in the Chromium DEPS file.
   'src/buildtools':
     Var('chromium_git') + '/chromium/buildtools.git' + '@' + '64e38f0cebdde27aa0cfb405f330063582f9ac76',
 
   # Entry only present in WebRTC, not Chromium.
   'src/third_party/gflags/src':
     Var('chromium_git') + '/external/github.com/gflags/gflags@03bebcb065c83beff83d50ae025a55a4bf94dfca',
 }
 
 deps_os = {
   # Entry only present in WebRTC, not Chromium.
   'win': {
-    'src/third_party/winsdk_samples/src':
+    'src/third_party/winsdk_samples':
       Var('chromium_git') + '/external/webrtc/deps/third_party/winsdk_samples_v71@e71b549167a665d7424d6f1dadfbff4b4aad1589',
   },
 }