Clean up stale java in explicit bindings generator gypi

third_party/mojo/mojom_bindings_generator_explicit.gypi

Index: third_party/mojo/mojom_bindings_generator_explicit.gypi
diff --git a/third_party/mojo/mojom_bindings_generator_explicit.gypi b/third_party/mojo/mojom_bindings_generator_explicit.gypi
index d03eb8547969a094a369812bfc98394a7a7ac876..f65ec3e30481ffbfd64316925f3d94a7a140f936 100644
--- a/third_party/mojo/mojom_bindings_generator_explicit.gypi
+++ b/third_party/mojo/mojom_bindings_generator_explicit.gypi
@@ -19,9 +19,26 @@
   # to be compiled with multiple toolchains - target, NaCl, etc.
   'actions': [
     {
+      'variables': {
+        'java_out_dir': '<(PRODUCT_DIR)/java_mojo/<(_target_name)/src',
+        'stamp_filename': '<(PRODUCT_DIR)/java_mojo/<(_target_name)/<(_target_name).stamp',
+      },
+      'action_name': '<(_target_name)_mojom_bindings_stamp',
+      # The java output directory is deleted to ensure that the java library
+      # doesn't try to compile stale files.
+      'action': [
+        'python', '<(DEPTH)/build/rmdir_and_stamp.py',
+        '<(java_out_dir)',
+        '<(stamp_filename)',
+      ],
+      'inputs': [ '<@(mojom_files)' ],
+      'outputs': [ '<(stamp_filename)' ],
+    },
+    {
       'action_name': '<(_target_name)_mojom_bindings_generator',
       'variables': {
         'java_out_dir': '<(PRODUCT_DIR)/java_mojo/<(_target_name)/src',
+        'stamp_filename': '<(PRODUCT_DIR)/java_mojo/<(_target_name)/<(_target_name).stamp',
         'mojom_import_args%': [
          '-I<(DEPTH)',
          '-I<(DEPTH)/third_party/mojo/src'
@@ -30,6 +47,7 @@
       'inputs': [
         '<@(mojom_bindings_generator_sources)',
         '<@(mojom_files)',
+        '<(stamp_filename)',
       ],
       'outputs': [
         '<@(mojom_generated_outputs)',
@@ -79,6 +97,10 @@
         'generated_src_dirs': [
           '<(PRODUCT_DIR)/java_mojo/<(_target_name)/src',
         ],
+        'additional_input_paths': [
+          '<@(mojom_bindings_generator_sources)',
+          '<@(mojom_files)',
+        ],
       },
     }
   },