Add more GN deps to the build.

tools/generate_library_loader/generate_library_loader.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.
+
+# name: Name to use for the value of the --name arg.

[awong, 2014/07/01 21:47:11]

Can we add a sentence or two explaining what as library_loader is and why you'd
use this template?

[brettw, 2014/07/01 23:26:27]

I added a brief one. I don't actually know any more than what I added.

[awong, 2014/07/01 23:30:46]

Huh...looking at this file more closely, it feels like we have duplicated
functionality between this an generate_sigs. Ah well. Whatever.

Thanks for the comment.

+# output_h/output_cc: Names for the generated header/cc file with no dir.
+# header: header file to process. Example: "<foo/bar.h>"
+# functions: List of strings for functions to process.
+# config: (optional) Label of the config generated by pkgconfig.
+# bundled_header: (optional)
+template("generate_library_loader") {
+  output_h = "$root_gen_dir/library_loaders/" + invoker.output_h
+  output_cc = "$root_gen_dir/library_loaders/" + invoker.output_cc
+
+  action_visibility = ":$target_name"
+  action("${target_name}_loader") {
+    visibility = action_visibility
+
+    script = "//tools/generate_library_loader/generate_library_loader.py"
+    if (defined(invoker.visibility)) {
+      visibility = invoker.visibility
+    }
+
+    outputs = [ output_h, output_cc ]
+
+    args = [
+      "--name", invoker.name,
+      "--output-h", rebase_path(output_h),
+      "--output-cc", rebase_path(output_cc),
+      "--header", invoker.header,
+      # Note GYP build exposes a per-target variable to control this, which, if
+      # manually set to true, will disable dlopen(). Its not clear this is
+      # needed, so here we just leave off. If this can be done globally, we can
+      # expose one switch for this value, otherwise we need to add a template
+      # param for this.
+      "--link-directly=0",
+    ]
+    if (defined(invoker.bundled_header)) {
+      args += [ "--bundled-header", invoker.bundled_header ]
+    }
+    args += invoker.functions
+  }
+
+  source_set(target_name) {
+    if (defined(invoker.config)) {
+      direct_dependent_configs = [ invoker.config ]
+    }
+    sources = [ output_h, output_cc ]
+    deps = [ ":${target_name}_loader" ]
+  }
+}