gclient DEPS file for auto checking out deps

Added a DEPS file so that bot_update and gclient can automatically check
out dependencies (GYP, V8, ICU, and on Windows, Cygwin).

BUG=375773
R=jam@chromium.org, nodir@chromium.org

Review URL: https://codereview.chromium.org/416663002

DEPS

diff --git a/DEPS b/DEPS
new file mode 100644
index 0000000..5a28c8d
--- /dev/null
+++ b/DEPS
@@ -0,0 +1,17 @@
+deps = {
+  "pdfium/build/gyp":
+    "https://chromium.googlesource.com/external/gyp",
+
+  "pdfium/v8":
+    "https://chromium.googlesource.com/external/v8",
+
+  "pdfium/v8/third_party/icu":
+    "https://chromium.googlesource.com/chromium/deps/icu46",
+}
+
+deps_os = {
+  "win": {
+    "pdfium/v8/third_party/cygwin":
+      "https://chromium.googlesource.com/chromium/deps/cygwin@c89e446b273697fadf3a10ff1007a97c0b7de6df",
+  },
+}