Turn //mojo/public/cpp/bindings and //mojo/public/cpp/system into components

mojo/public/tools/bindings/mojom.gni

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 mojom_generator_root = "//mojo/public/tools/bindings"
 mojom_generator_script = "$mojom_generator_root/mojom_bindings_generator.py"
 mojom_generator_sources = [
   "$mojom_generator_root/generators/mojom_cpp_generator.py",
   "$mojom_generator_root/generators/mojom_js_generator.py",
   "$mojom_generator_root/generators/mojom_java_generator.py",
@@ skipping 186 matching lines @@
       deps += [ ":$generator_shared_target_name" ]
     }
     public_deps = []
     foreach(d, all_deps) {
       # Resolve the name, so that a target //mojo/something becomes
       # //mojo/something:something and we can append shared_cpp_sources_suffix
       # to get the cpp dependency name.
       full_name = get_label_info("$d", "label_no_toolchain")
       public_deps += [ "${full_name}_${shared_cpp_sources_suffix}" ]
     }
+    defines = []
+    if (defined(invoker.export_define)) {
+      defines += [ invoker.export_define ]

[yzshen1, 2016/09/22 18:26:27]

Why this is needed?

[yzshen1, 2016/09/22 18:34:10]

Just saw your comments. Let me think about it some more...

[yzshen1, 2016/09/22 19:39:36]

It seems a little hacky because invoker.export_define is for the "chromium
variant" while this shared_cpp_sources is used by both the "chromium variant"
and "blink variant". 

I think another possible solution is to make mojo/public/cpp/bindings depends on
mojo/public/interfaces/bindings:bindings__generator (which just generates
files), and then explicitly adds those generated files into the sources section
of mojo/public/cpp/bindings.
Because this is a very special case, I think maybe it is fine to be verbose.

WDYT? Thanks!

[dcheng, 2016/09/22 22:18:21]

It's very hacky. I like your solution better. =)

+    }
   }
 
   # Generate code for variants.
   foreach(bindings_configuration, _bindings_configurations) {
     cpp_only = false
     variant_suffix = ""
     if (defined(bindings_configuration.variant)) {
       variant = bindings_configuration.variant
       variant_suffix = "_${variant}"
       cpp_only = true
@@ skipping 309 matching lines @@
           full_name = get_label_info(d, "label_no_toolchain")
           deps += [ "${full_name}_java" ]
         }
 
         srcjar_deps = [ ":$java_srcjar_target_name" ]
         run_findbugs_override = false
       }
     }
   }
 }