Add hooks to get the GN binaries in buildtools.

DEPS

Index: DEPS
diff --git a/DEPS b/DEPS
index 7a70478a69d81b2162f2f2c527643300bc3ad6a2..1e7e43fb15123bd581b1eed474ff2ac03390424b 100644
--- a/DEPS
+++ b/DEPS
@@ -662,7 +662,7 @@ hooks = [
                 "--platform=win32",
                 "--no_auth",
                 "--bucket", "chromium-gn",
-                "-s", "src/tools/gn/bin/win/gn.exe.sha1",
+                "-s", "src/buildtools/win/gn.exe.sha1",
     ],
   },
   {
@@ -673,11 +673,57 @@ hooks = [
                 "--platform=darwin",
                 "--no_auth",
                 "--bucket", "chromium-gn",
+                "-s", "src/buildtools/mac/gn.sha1",
+    ],
+  },
+  {
+    "name": "gn_linux32",
+    "pattern": ".",
+    "action": [ "download_from_google_storage",
+                "--no_resume",
+                "--platform=linux*",
+                "--no_auth",
+                "--bucket", "chromium-gn",
+                "-s", "src/buildtools/linux32/gn.sha1",
+    ],
+  },
+  {
+    "name": "gn_linux64",
+    "pattern": ".",
+    "action": [ "download_from_google_storage",
+                "--no_resume",
+                "--platform=linux*",
+                "--no_auth",
+                "--bucket", "chromium-gn",
+                "-s", "src/buildtools/linux64/gn.sha1",
+    ],
+  },
+  # Pull GN binaries (old location). TODO(brettw) remove this after a transition
+  # period while we move the binaries from tools/gn/bin to buildtools.
+  {
+    "name": "gn_old_win",
+    "pattern": ".",
+    "action": [ "download_from_google_storage",
+                "--no_resume",
+                "--platform=win32",
+                "--no_auth",
+                "--bucket", "chromium-gn",
+                "-s", "src/tools/gn/bin/win/gn.exe.sha1",
+    ],
+  },
+  {
+    "name": "gn_old_mac",
+    "pattern": ".",
+    "action": [ "download_from_google_storage",
+                "--no_resume",
+                "--platform=darwin",
+                "--no_auth",
+                "--bucket", "chromium-gn",
                 "-s", "src/tools/gn/bin/mac/gn.sha1",
     ],
   },
   {
-    "name": "gn_linux",
+    "name": "gn_old_linux",
     "pattern": ".",
     "action": [ "download_from_google_storage",
                 "--no_resume",
@@ -688,7 +734,7 @@ hooks = [
     ],
   },
   {
-    "name": "gn_linux32",
+    "name": "gn_old_linux32",
     "pattern": ".",
     "action": [ "download_from_google_storage",
                 "--no_resume",