Add java_cpp_template template

build/config/android/rules.gni

Index: build/config/android/rules.gni
diff --git a/build/config/android/rules.gni b/build/config/android/rules.gni
index 850f13e44beb58fda74fcd1954155390448007d9..abf64a1c4044cc5e048e92248fa8f778363cbd25 100644
--- a/build/config/android/rules.gni
+++ b/build/config/android/rules.gni
@@ -2,6 +2,8 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("internal_rules.gni")
+
 # Declare a jni target
 #
 # This target generates the native jni bindings for a set of .java files.
@@ -57,3 +59,83 @@ template("generate_jni") {
     }
   }
 }
+
+# Declare a target for c-preprocessor-generated java files
+#
+# This target generates java files using the host C pre-processor. Each file in
+# sources will be compiled using the C pre-processor. If include_path is
+# specified, it will be passed (with --I) to the pre-processor.
+#
+# This target will create a single .srcjar. Adding this target to a library
+# target's srcjar_deps will make the generated java files be included in that
+# library's final outputs.
+#
+# Variables
+#   sources: list of files to be processed by the C pre-processor. For each
+#     file in sources, there will be one .java file in the final .srcjar. For a
+#     file named FooBar.template, a java file will be created with name
+#     FooBar.java.
+#   source_prereqs: additional compile-time dependencies. Any files
+#     `#include`-ed in the templates should be listed here.
+#   package_name: this will be the subdirectory for each .java file in the .srcjar.
+#
+# Example
+#   java_cpp_template("foo_generated_enum") {
+#     sources = [
+#       "android/java/templates/Foo.template",
+#     ]
+#     source_prereqs = [
+#       "android/java/templates/native_foo_header.h",
+#     ]
+#
+#     package_name = "org/chromium/base/library_loader"
+#     include_path = "android/java/templates"
+#   }
+template("java_cpp_template") {
+  assert(defined(invoker.sources))
+  package_name = invoker.package_name + ""
+
+  if (defined(invoker.include_path)) {
+    include_path = invoker.include_path + ""
+  } else {
+    include_path = "//"
+  }
+
+  action_foreach("${target_name}__apply_gcc") {
+    script = "//build/android/gyp/gcc_preprocess.py"
+    if (defined(invoker.source_prereqs)) {
+      source_prereqs = invoker.source_prereqs + []
+    }
+
+    sources = invoker.sources
+
+    gen_dir = "${target_gen_dir}/${package_name}"
+    gcc_template_output_pattern = "${gen_dir}/{{source_name_part}}.java"
+
+    outputs = [
+      gcc_template_output_pattern
+    ]
+
+    args = [
+      "--include-path", rebase_path(include_path, root_build_dir),
+      "--output", rebase_path(gen_dir, root_build_dir) + "/{{source_name_part}}.java",
+      "--template={{source}}",
+    ]
+  }
+
+  apply_gcc_outputs = get_target_outputs(":${target_name}__apply_gcc")
+  base_gen_dir = get_label_info(":${target_name}__apply_gcc", "target_gen_dir")
+
+  srcjar_path = "${target_gen_dir}/${target_name}.srcjar"
+  zip("${target_name}__zip_srcjar") {
+    inputs = apply_gcc_outputs
+    output = srcjar_path
+    base_dir = base_gen_dir
+  }
+
+  group(target_name) {
+    deps = [
+      ":${target_name}__zip_srcjar"
+    ]
+  }
+}