Support exporting Mojo bindings for the component build.

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 60 matching lines @@
 #   visibility (optional)
 #
 #   use_new_wrapper_types (optional)
 #       If set to true, mojom array/map/string will be mapped to STL (for
 #       chromium variant) or WTF (for blink) types. Otherwise, they will be
 #       mapped to mojo::Array/Map/String/etc.
 #       Default value is true.
 #       TODO(yzshen):
 #         - convert all users to use the new mode;
 #         - remove support for the old mode.
+#
+# The following parameters are used to support the component build. They are
+# needed so that bindings which are linked with a component can use the same
+# export settings for classes. The first three are for the chromium variant, and
+# the last three are for the blink variant.
+#   export_class_attribute (optional)
+#       The attribute to add to the class declaration. e.g. "CONTENT_EXPORT"
+#   export_define (optional)
+#       A define to be added to the source_set which is needed by the export
+#       header. e.g. "CONTENT_IMPLEMENTATION=1"
+#   export_header (optional)
+#       A header to be added to the generated bindings to support the component
+#       build. e.g. "content/common/content_export.h"
+#   export_class_attribute_blink (optional)
+#   export_define_blink (optional)
+#   export_header_blink (optional)
+#       These three parameters are the blink variants of the previous 3.
 template("mojom") {
   assert(
       defined(invoker.sources) || defined(invoker.deps) ||
           defined(invoker.public_deps),
       "\"sources\" or \"deps\" must be defined for the $target_name template.")
+  if (defined(invoker.export_class_attribute) ||
+      defined(invoker.export_define) || defined(invoker.export_header)) {
+    assert(defined(invoker.export_class_attribute))
+    assert(defined(invoker.export_define))
+    assert(defined(invoker.export_header))
+  }
+  if (defined(invoker.export_class_attribute_blink) ||
+      defined(invoker.export_define_blink) ||
+      defined(invoker.export_header_blink)) {
+    assert(defined(invoker.export_class_attribute_blink))
+    assert(defined(invoker.export_define_blink))
+    assert(defined(invoker.export_header_blink))
+  }
 
   all_deps = []
   if (defined(invoker.deps)) {
     all_deps += invoker.deps
   }
   if (defined(invoker.public_deps)) {
     all_deps += invoker.public_deps
   }
 
   group("${target_name}__is_mojom") {
@@ skipping 130 matching lines @@
 
         if (defined(bindings_configuration.for_blink) &&
             bindings_configuration.for_blink) {
           args += [ "--for_blink" ]
         }
 
         if (!defined(invoker.use_new_wrapper_types) ||
             invoker.use_new_wrapper_types) {
           args += [ "--use_new_wrapper_types" ]
         }
+        if (defined(invoker.export_class_attribute) &&

[yzshen1, 2016/08/08 17:07:32]

It seems simpler to merge these new if's with line 257-260:

if (defined(bindings_configuration.for_blink) &&
    bindings_configuration.for_blink) {
  args += [ "--for_blink" ]
  if (defined(invoker.export_class_attribute_blink)) {
    args += [
      "--export_attribute",
      invoker.export_class_attribute_blink,
      "--export_header",
      invoker.export_header_blink,
    ]
  }
} else {
  # add the chromium export_attributes and export header, if defined.
  ...
}

[jam, 2016/08/08 17:36:08]

Done.

+            !defined(bindings_configuration.variant)) {
+          args += [
+            "--export_attribute",
+            invoker.export_class_attribute,
+          ]
+        }
+        if (defined(invoker.export_class_attribute_blink) &&
+            defined(bindings_configuration.for_blink)) {
+          args += [
+            "--export_attribute",
+            invoker.export_class_attribute_blink,
+          ]
+        }
+        if (defined(invoker.export_header) &&
+            !defined(bindings_configuration.variant)) {
+          args += [
+            "--export_header",
+            invoker.export_header,
+          ]
+        }
+        if (defined(invoker.export_header_blink) &&
+            defined(bindings_configuration.for_blink)) {
+          args += [
+            "--export_header",
+            invoker.export_header_blink,
+          ]
+        }
       }
     }
 
     action(type_mappings_target_name) {
       inputs = _bindings_configuration_files
       outputs = [
         type_mappings_path,
       ]
       script = "$mojom_generator_root/generate_type_mappings.py"
       deps = []
@@ skipping 72 matching lines @@
       }
     }
 
     # The generated C++ source files. The main reason to introduce this target
     # is so that mojo/public/cpp/bindings can depend on mojom interfaces without
     # circular dependencies. It means that the target is missing the dependency
     # on mojo/public/cpp/bindings. No external targets should depend directly on
     # this target *except* mojo/public/cpp/bindings and other *_cpp_sources
     # targets.
     source_set(cpp_sources_target_name) {
+      defines = []
       if (defined(invoker.testonly)) {
         testonly = invoker.testonly
       }
+      if (defined(invoker.export_define)) {
+        defines += [ invoker.export_define ]
+      }
+      if (defined(invoker.export_define_blink)) {
+        defines += [ invoker.export_define_blink ]
+      }
       if (enabled_sources != []) {
         sources = process_file_template(enabled_sources, generator_cpp_outputs)
       }
       deps = [
         "//mojo/public/cpp/bindings:struct_traits",
         "//mojo/public/interfaces/bindings:bindings__generator",
       ]
       if (enabled_sources != []) {
         deps += [ ":$generator_target_name" ]
       }
@@ skipping 74 matching lines @@
           full_name = get_label_info(d, "label_no_toolchain")
           deps += [ "${full_name}_java" ]
         }
 
         srcjar_deps = [ ":$java_srcjar_target_name" ]
         run_findbugs_override = false
       }
     }
   }
 }