Merge to XFA: Make checkdeps --resolve-dotdot succeed.

DEPS

 use_relative_paths = True
 
 deps = {
   "build/gyp":
     "https://chromium.googlesource.com/external/gyp",
 
   "buildtools":
     "https://chromium.googlesource.com/chromium/buildtools.git@46ce8cb60364e9e0b21a81136c7debdddfd063a8",
 
   "testing/corpus":
@@ skipping 16 matching lines @@
 }
 
 deps_os = {
   "win": {
     "v8/third_party/cygwin":
       "https://chromium.googlesource.com/chromium/deps/cygwin@c89e446b273697fadf3a10ff1007a97c0b7de6df",
   },
 }
 
 include_rules = [
+  # Basic stuff that everyone can use.
+  # Note: public is not here because core cannot depend on public.
   '+testing',
   '+third_party/base',
 ]
 
 hooks = [
   {
     # A change to a .gyp, .gypi, or to GYP itself should run the generator.
     'name': 'gyp',
     'pattern': '.',
     'action': ['python', 'pdfium/build/gyp_pdfium'],
@@ skipping 32 matching lines @@
                 '-s', 'pdfium/buildtools/linux64/clang-format.sha1',
     ],
   },
   {
     # Pull clang if needed or requested via GYP_DEFINES.
     'name': 'clang',
     'pattern': '.',
     'action': ['python', 'pdfium/tools/clang/scripts/update.py', '--if-needed'],
   },
 ]