Generate protobuf classes at build-time.

This method is well-established in Chromium. The new code is largely boilerplate copied from there. The advantage is that we don't have to maintain various versions of the classes; we just generate against whatever compiler version happens to exist at build-time.
Review URL: http://webrtc-codereview.appspot.com/93008

git-svn-id: http://webrtc.googlecode.com/svn/trunk@271 4adac7df-926f-26a2-2b94-8c16560cd09d

src/modules/audio_processing/main/apm_tests.gyp

@@ -10,6 +10,9 @@
   'includes': [
     '../../../common_settings.gypi',
   ],
+  'variables': {
+    'protoc_out_dir': '<(SHARED_INTERMEDIATE_DIR)/protoc_out',
+  },
   'targets': [
     {
       'target_name': 'unit_test',
@@ -22,30 +25,67 @@
         }],
       ],
       'dependencies': [
+        'apm_unittest_proto',
         'source/apm.gyp:audio_processing',
-        '../../../system_wrappers/source/system_wrappers.gyp:system_wrappers',
         '../../../common_audio/signal_processing_library/main/source/spl.gyp:spl',
-
+        '../../../system_wrappers/source/system_wrappers.gyp:system_wrappers',
         '../../../../testing/gtest.gyp:gtest',
         '../../../../testing/gtest.gyp:gtest_main',
         '../../../../third_party/protobuf/protobuf.gyp:protobuf_lite',
       ],
       'include_dirs': [
         '../../../../testing/gtest/include',
+        '<(protoc_out_dir)',
       ],
       'sources': [
         'test/unit_test/unit_test.cc',
-        'test/unit_test/audio_processing_unittest.pb.cc',
-        'test/unit_test/audio_processing_unittest.pb.h',
+        '<(protoc_out_dir)/audio_processing_unittest.pb.cc',
+        '<(protoc_out_dir)/audio_processing_unittest.pb.h',
       ],
     },
+    {
+      # Protobuf compiler / generate rule for unit_test
+      'target_name': 'apm_unittest_proto',
+      'type': 'none',
+      'variables': {
+        'proto_relpath': 'test/unit_test',
+      },
+      'sources': [
+        '<(proto_relpath)/audio_processing_unittest.proto',
+      ],
+      'rules': [
+        {
+          'rule_name': 'genproto',
+          'extension': 'proto',
+          'inputs': [
+            '<(PRODUCT_DIR)/<(EXECUTABLE_PREFIX)protoc<(EXECUTABLE_SUFFIX)',
+          ],
+          'outputs': [
+            '<(protoc_out_dir)/<(RULE_INPUT_ROOT).pb.cc',
+            '<(protoc_out_dir)/<(RULE_INPUT_ROOT).pb.h',
+          ],
+          'action': [
+            '<(PRODUCT_DIR)/<(EXECUTABLE_PREFIX)protoc<(EXECUTABLE_SUFFIX)',
+            '--proto_path=<(proto_relpath)',
+            '<(proto_relpath)/<(RULE_INPUT_NAME)',
+            '--cpp_out=<(protoc_out_dir)',
+          ],
+          'message': 'Generating C++ code from <(RULE_INPUT_PATH)',
+        },
+      ],
+      'dependencies': [
+        '../../../../third_party/protobuf/protobuf.gyp:protoc#host',
+      ],
+      # This target exports a hard dependency because it generates header
+      # files.
+      'hard_dependency': 1,
+    },
     {
       'target_name': 'process_test',
       'type': 'executable',
       'dependencies': [
         'source/apm.gyp:audio_processing',
         '../../../system_wrappers/source/system_wrappers.gyp:system_wrappers',
-
         '../../../../testing/gtest.gyp:gtest',
         '../../../../testing/gtest.gyp:gtest_main',
       ],

src/modules/audio_processing/main/source/apm.gyp

@@ -8,7 +8,7 @@
 
 {
   'includes': [
-    '../../../../common_settings.gypi', # Common settings
+    '../../../../common_settings.gypi',
   ],
   'targets': [
     {
@@ -18,18 +18,18 @@
         ['prefer_fixed_point==1', {
           'dependencies': ['../../ns/main/source/ns.gyp:ns_fix'],
           'defines': ['WEBRTC_NS_FIXED'],
-        }, { # else: prefer_fixed_point==0
+        }, {
           'dependencies': ['../../ns/main/source/ns.gyp:ns'],
           'defines': ['WEBRTC_NS_FLOAT'],
         }],
       ],
       'dependencies': [
-        '../../../../system_wrappers/source/system_wrappers.gyp:system_wrappers',
         '../../aec/main/source/aec.gyp:aec',
         '../../aecm/main/source/aecm.gyp:aecm',
         '../../agc/main/source/agc.gyp:agc',
         '../../../../common_audio/signal_processing_library/main/source/spl.gyp:spl',
         '../../../../common_audio/vad/main/source/vad.gyp:vad',
+        '../../../../system_wrappers/source/system_wrappers.gyp:system_wrappers',
       ],
       'include_dirs': [
         '../interface',