Fix missing files found by gn gen --check.

DEPS

 use_relative_paths = True
 
 vars = {
   'chromium_git': 'https://chromium.googlesource.com',
   'pdfium_git': 'https://pdfium.googlesource.com',
 
   'android_ndk_revision': '5022f40f12953c02b2614c5f7beb981ec5d0e833',
   'build_revision': '76d9f8b4fcae07fb82f28295468cf92bade935bd',
   'buildtools_revision': 'db6179b29f90d28026b0cb23ef71d56ec31b8bd6',
   'catapult_revision': '327256cb1c387e62a2c7e6960e2398867665fb51',
   'clang_revision': '797371be0a75c9892d6acb486d0430915ea538a6',
   'cygwin_revision': 'c89e446b273697fadf3a10ff1007a97c0b7de6df',
   'gen_library_loader_revision': '916d4acd8b2cde67a390737dfba90b3c37de23a1',
   'gmock_revision': '29763965ab52f24565299976b936d1265cb6a271',
   'gtest_revision': '8245545b6dc9c4703e6496d1efd19e975ad2b038',
   'icu_revision': '2341038bf72869a5683a893a2b319a48ffec7f62',
   'pdfium_tests_revision': '5867fa68fa3e00016d3e31374e84eb01a3db6ac7',
   'skia_revision': '3bf7509c3f68aefbe5f8b2ea5888319a71a91d2d',
   'tools_memory_revision': '427f10475e1a8d72424c29d00bf689122b738e5d',
   'trace_event_revision': '54b8455be9505c2cb0cf5c26bb86739c236471aa',
   'v8_revision': '75f10f91b1b0b392d2a29a7a480bf079db6f43fa',
 }
 
 deps = {
+  "base/trace_event/common":
+    Var('chromium_git') + "/chromium/src/base/trace_event/common.git@" +
+        Var('trace_event_revision'),
+
   "build":
     Var('chromium_git') + "/chromium/src/build.git@" + Var('build_revision'),
 
   "buildtools":
     Var('chromium_git') + "/chromium/buildtools.git@" + Var('buildtools_revision'),
 
   "testing/corpus":
     Var('pdfium_git') + "/pdfium_tests@" + Var('pdfium_tests_revision'),
 
   "testing/gmock":
@@ skipping 18 matching lines @@
   # TODO(GYP): Remove this when no tools rely on GYP anymore.
   "tools/gyp":
     Var('chromium_git') + '/external/gyp.git' + '@' + 'c61b0b35c8396bfd59efc6cfc11401d912b0f510',
 
   "tools/memory":
     Var('chromium_git') + "/chromium/src/tools/memory@" +
         Var('tools_memory_revision'),
 
   "v8":
     Var('chromium_git') + "/v8/v8.git@" + Var('v8_revision'),
-
-  "v8/base/trace_event/common":
-    Var('chromium_git') + "/chromium/src/base/trace_event/common.git@" +
-        Var('trace_event_revision'),
 }
 
 deps_os = {
   "android": {
     "third_party/android_ndk":
       Var('chromium_git') + "/android_ndk.git@" + Var('android_ndk_revision'),
     "third_party/catapult":
       Var('chromium_git') + "/external/github.com/catapult-project/catapult.git@" + Var('catapult_revision'),
   },
   "win": {
@@ skipping 105 matching lines @@
                '--if-needed'
     ],
   },
   {
     # Update the Windows toolchain if necessary.
     'name': 'win_toolchain',
     'pattern': '.',
     'action': ['python', 'pdfium/build/vs_toolchain.py', 'update'],
   },
 ]