Add support for proguard preprocessing.

build/java.gypi

Index: build/java.gypi
diff --git a/build/java.gypi b/build/java.gypi
index 1635c71da40db66cfee1a1737cc9089057ec378c..5318e2a35983cd4857cdd20b8770439db160fbd9 100644
--- a/build/java.gypi
+++ b/build/java.gypi
@@ -70,6 +70,21 @@
     'intermediate_dir': '<(SHARED_INTERMEDIATE_DIR)/<(_target_name)',
     'classes_dir': '<(intermediate_dir)/classes',
     'compile_stamp': '<(intermediate_dir)/compile.stamp',
+    'proguard_config%': '',
+    'proguard_preprocess%': '0',
+    'variables': {
+      'variables': {
+        'proguard_preprocess%': 0,
+      },
+      'conditions': [
+        ['proguard_preprocess == 1', {
+          'javac_jar_path': '<(intermediate_dir)/<(_target_name).pre.jar'
+        }, {
+          'javac_jar_path': '<(PRODUCT_DIR)/lib.java/<(jar_name)'
+        }],
+      ],
+    },
+    'javac_jar_path': '<(javac_jar_path)',
   },
   # This all_dependent_settings is used for java targets only. This will add the
   # jar path to the classpath of dependent java targets.
@@ -218,6 +233,35 @@
         },
       ],
     }],
+    ['proguard_preprocess == 1', {
+      'actions': [
+        {
+          'action_name': 'proguard_<(_target_name)',
+          'message': 'Proguard preprocessing <(_target_name) jar',
+          'inputs': [
+            '<(android_sdk_root)/tools/proguard/bin/proguard.sh',
+            '<(DEPTH)/build/android/gyp/util/build_utils.py',
+            '<(DEPTH)/build/android/gyp/proguard.py',
+            '<(javac_jar_path)',
+            '<(proguard_config)',
+          ],
+          'outputs': [
+            '<(jar_path)',
+          ],
+          'action': [
+            'python', '<(DEPTH)/build/android/gyp/proguard.py',
+            '--proguard-path=<(android_sdk_root)/tools/proguard/bin/proguard.sh',
+            '--input-path=<(javac_jar_path)',
+            '--output-path=<(jar_path)',
+            '--proguard-config=<(proguard_config)',
+            '--classpath=<(android_sdk_jar) >(input_jars_paths)',
+
+            # TODO(newt): remove this once http://crbug.com/177552 is fixed in ninja.
+            '--ignore=>!(echo \'>(_inputs)\' | md5sum)',
+          ]
+        },
+      ],
+    }],
   ],
   'actions': [
     {
@@ -263,12 +307,12 @@
         '<(compile_stamp)',
       ],
       'outputs': [
-        '<(jar_path)',
+        '<(javac_jar_path)',
       ],
       'action': [
         'python', '<(DEPTH)/build/android/gyp/jar.py',
         '--classes-dir=<(classes_dir)',
-        '--jar-path=<(jar_path)',
+        '--jar-path=<(javac_jar_path)',
         '--excluded-classes=<(jar_excluded_classes)',
 
         # TODO(newt): remove this once http://crbug.com/177552 is fixed in ninja.