Fix missing GN dependencies.

build/json_schema_api.gni

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Defines a static library corresponding to the output of schema compiler tools
 # over a set of extensions API schemas (IDL or JSON format.) The library target
 # has implicit hard dependencies on all schema files listed by the invoker and
 # is itself a hard dependency.
 #
 # Invocations of this template may use the following variables:
@@ skipping 136 matching lines @@
   }
 
   if (bundle_registration) {
     uncompiled_sources = []
     if (defined(invoker.uncompiled_sources)) {
       uncompiled_sources = invoker.uncompiled_sources
     }
 
     assert(defined(invoker.impl_dir),
            "\"impl_dir\" must be defined for the $target_name template.")
-    impl_dir = invoker.impl_dir
+
+    # Child directory inside the generated file tree.
+    gen_child_dir = rebase_path(invoker.impl_dir, "//")
 
     bundle_generator_registration_name =
         target_name + "_bundle_generator_registration"
     action(bundle_generator_registration_name) {
       script = compiler_script
       inputs = compiler_sources + invoker.sources + uncompiled_sources
       outputs = [
-        "$root_gen_dir/$impl_dir/generated_api_registration.cc",
-        "$root_gen_dir/$impl_dir/generated_api_registration.h",
+        "$root_gen_dir/$gen_child_dir/generated_api_registration.cc",
+        "$root_gen_dir/$gen_child_dir/generated_api_registration.h",
       ]
       args = [
                "--root=" + rebase_path("//", root_build_dir),
                "--destdir=" + rebase_path(root_gen_dir, root_build_dir),
                "--namespace=$root_namespace",
                "--generator=cpp-bundle-registration",
-               "--impl-dir=" + rebase_path(impl_dir, "//"),
+               "--impl-dir=$gen_child_dir",
                "--include-rules=$schema_include_rules",
              ] + rebase_path(invoker.sources, root_build_dir) +
              rebase_path(uncompiled_sources, root_build_dir)
     }
   }
 
   # Compute the contents of the library/source set.
   lib_sources = invoker.sources
   lib_deps = []
   lib_public_deps = []
@@ skipping 47 matching lines @@
 
       if (defined(invoker.visibility)) {
         visibility = invoker.visibility
       }
       if (defined(invoker.output_name)) {
         output_name = invoker.output_name
       }
     }
   }
 }