GN: Use interface jars in the classpath to speed up compiling (a little)

Rebuilding chrome_java before change:
real    1m0.108s
user    7m44.609s
sys     0m27.630s

Rebuilding chrome_java after change:
real    0m57.893s
user    7m22.493s
sys     0m21.224s

BUG=527632

Review URL: https://codereview.chromium.org/1328823002

Cr-Original-Commit-Position: refs/heads/master@{#347405}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 6d6c9ac82e8f06abb047501d37b95cae145a727c

android/BUILD.gn

@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 import("//build/config/android/rules.gni")
+import("//third_party/ijar/ijar.gni")
 
 sun_tools_jar_path = "$root_gen_dir/sun_tools_jar/tools.jar"
 
@@ -26,6 +27,11 @@ java_prebuilt("sun_tools_java") {
   jar_dep = ":find_sun_tools_jar"
 }
 
+generate_interface_jar("android_ijar") {
+  input_jar = android_sdk_jar
+  output_jar = "$root_out_dir/lib.java/android.interface.jar"
+}
+
 action("cpplib_stripped") {
   _strip_bin = "${android_tool_prefix}strip"
   _soname = "libc++_shared.so"

android/gyp/javac.py

@@ -132,6 +132,10 @@ def _ParseOptions(argv):
       action='append',
       help='Classpath for javac. If this is specified multiple times, they '
       'will all be appended to construct the classpath.')
+  parser.add_option(
+      '--use-ijars',
+      action='store_true',
+      help='Whether to use interface jars (.interface.jar) when compiling')
   parser.add_option(
       '--javac-includes',
       default='',
@@ -201,12 +205,19 @@ def main(argv):
 
   java_files = _FilterJavaFiles(java_files, options.javac_includes)
 
+  runtime_classpath = options.classpath
+  compile_classpath = runtime_classpath
+  if options.use_ijars:
+    ijar_re = re.compile(r'\.jar$')
+    compile_classpath = (
+        [ijar_re.sub('.interface.jar', p) for p in runtime_classpath])
+
   javac_args = [
       '-g',
       # Chromium only allows UTF8 source files.  Being explicit avoids
       # javac pulling a default encoding from the user's environment.
       '-encoding', 'UTF-8',
-      '-classpath', ':'.join(options.classpath),
+      '-classpath', ':'.join(compile_classpath),
       ]
 
   if options.bootclasspath:
@@ -231,11 +242,13 @@ def main(argv):
 
   # Compute the list of paths that when changed, we need to rebuild.
   input_paths = options.bootclasspath + options.java_srcjars + java_files
-  for path in options.classpath:
-    if os.path.exists(path + '.TOC'):
-      input_paths.append(path + '.TOC')
-    else:
-      input_paths.append(path)
+  # TODO(agrieve): Remove this .TOC heuristic once GYP is no more.
+  if not options.use_ijars:
+    for path in compile_classpath:
+      if os.path.exists(path + '.TOC'):
+        input_paths.append(path + '.TOC')
+      else:
+        input_paths.append(path)
   python_deps = build_utils.GetPythonDependencies()
 
   def OnStaleMd5():
@@ -266,7 +279,7 @@ def main(argv):
         if options.manifest_entry:
           entries = [e.split(':') for e in options.manifest_entry]
         manifest_file = os.path.join(temp_dir, 'manifest')
-        _CreateManifest(manifest_file, options.classpath, options.main_class,
+        _CreateManifest(manifest_file, runtime_classpath, options.main_class,
                         entries)
       else:
         manifest_file = None

config/android/internal_rules.gni

@@ -413,7 +413,8 @@ template("process_java_prebuilt") {
 
   _input_jar_path = invoker.input_jar_path
   _output_jar_path = invoker.output_jar_path
-  _jar_toc_path = _output_jar_path + ".TOC"
+  _output_ijar_path = get_path_info(_output_jar_path, "dir") + "/" +
+                      get_path_info(_output_jar_path, "name") + ".interface.jar"
 
   assert(invoker.build_config != "")
 
@@ -477,10 +478,9 @@ template("process_java_prebuilt") {
     }
   }
 
-  # TODO(agrieve): Change file extension to .ijar and use them in classpaths.
-  generate_interface_jar("${target_name}__jar_toc") {
+  generate_interface_jar("${target_name}__ijar") {
     input_jar = _output_jar_path
-    output_jar = _jar_toc_path
+    output_jar = _output_ijar_path
     deps = [
       ":$_output_jar_target",
     ]
@@ -489,7 +489,7 @@ template("process_java_prebuilt") {
   group(target_name) {
     forward_variables_from(invoker, [ "visibility" ])
     public_deps = [
-      ":${target_name}__jar_toc",
+      ":${target_name}__ijar",
       ":$_output_jar_target",
     ]
   }
@@ -984,7 +984,7 @@ template("java_prebuilt_impl") {
 #
 # Outputs:
 #  $jar_path.jar
-#  $jar_path.jar.TOC
+#  $jar_path.interface.jar
 #
 # Variables
 #   java_files: List of .java files to compile.
@@ -1083,6 +1083,7 @@ template("compile_java") {
     _rebased_depfile = rebase_path(depfile, root_build_dir)
     args = [
       "--depfile=$_rebased_depfile",
+      "--use-ijars",
       "--classpath=@FileArg($_rebased_build_config:javac:classpath)",
       "--jar-path=$_rebased_jar_path",
       "--java-srcjars=$_rebased_java_srcjars",
@@ -1090,8 +1091,11 @@ template("compile_java") {
       "--jar-excluded-classes=$_jar_excluded_patterns",
     ]
     if (_supports_android) {
-      _rebased_android_sdk_jar = rebase_path(android_sdk_jar, root_build_dir)
-      args += [ "--bootclasspath=$_rebased_android_sdk_jar" ]
+      deps += [ "//build/android:android_ijar" ]
+      _android_sdk_ijar = "$root_out_dir/lib.java/android.interface.jar"
+      inputs += [ _android_sdk_ijar ]
+      _rebased_android_sdk_ijar = rebase_path(_android_sdk_ijar, root_build_dir)
+      args += [ "--bootclasspath=$_rebased_android_sdk_ijar" ]
     }
     foreach(e, _manifest_entries) {
       args += [ "--manifest-entry=" + e ]