Plugin support for protobuf compiler (protoc) targets.

build/protoc.gypi

Index: build/protoc.gypi
diff --git a/build/protoc.gypi b/build/protoc.gypi
index fafdf9df7ab5c5e49a7825750f900de20d20ea7c..4e67b5b1f7135abd10eee95f3b297ce9a2b556f3 100644
--- a/build/protoc.gypi
+++ b/build/protoc.gypi
@@ -52,6 +52,7 @@
     'cc_dir': '<(SHARED_INTERMEDIATE_DIR)/protoc_out/<(proto_out_dir)',
     'py_dir': '<(PRODUCT_DIR)/pyproto/<(proto_out_dir)',
     'cc_generator_options%': '',
+    'cc_generator_plugin%': '',
     'cc_include%': '',
     'proto_in_dir%': '.',
     'conditions': [
@@ -88,6 +89,7 @@
         # Naively you'd use <(RULE_INPUT_PATH) here, but protoc requires
         # --proto_path is a strict prefix of the path given as an argument.
         '--proto-in-file','<(RULE_INPUT_ROOT)<(RULE_INPUT_EXT)',
+        '--cc-generator-plugin=<(cc_generator_plugin)',
         '--use-system-protobuf=<(use_system_protobuf)',
         '--',
         '<(protoc)',
@@ -100,7 +102,6 @@
   ],
   'dependencies': [
     '<(DEPTH)/third_party/protobuf/protobuf.gyp:protoc#host',
-    '<(DEPTH)/third_party/protobuf/protobuf.gyp:protobuf_lite',
   ],
   'include_dirs': [
     '<(SHARED_INTERMEDIATE_DIR)/protoc_out',
@@ -112,12 +113,18 @@
       '<(DEPTH)',
     ]
   },
-  'export_dependent_settings': [
-    # The generated headers reference headers within protobuf_lite,
-    # so dependencies must be able to find those headers too.
-    '<(DEPTH)/third_party/protobuf/protobuf.gyp:protobuf_lite',
-  ],
-  # This target exports a hard dependency because it generates header
-  # files.
+  # If using built-in cc generator the resulting headers reference headers
+  # within protobuf_lite, hence dependencies require those headers too.
+  # In case of generator plugin such issues should be resolved by invoker.
   'hard_dependency': 1,
+  'conditions': [
+    ['cc_generator_plugin==""', {
+      'dependencies': [
+        '<(DEPTH)/third_party/protobuf/protobuf.gyp:protobuf_lite',
+      ],
+      'export_dependent_settings': [
+        '<(DEPTH)/third_party/protobuf/protobuf.gyp:protobuf_lite',
+      ],
+    }],
+  ],
 }