Add a mojoPrivate API that exposes mojo to component apps/extensions.

extensions/renderer/module_system.cc

Index: extensions/renderer/module_system.cc
diff --git a/extensions/renderer/module_system.cc b/extensions/renderer/module_system.cc
index 5a180b458583040c3ee433656abb7b1df74f3f89..eebc451a89ed21230063ddd87646cfbb29adcb39 100644
--- a/extensions/renderer/module_system.cc
+++ b/extensions/renderer/module_system.cc
@@ -657,17 +657,20 @@ v8::Handle<v8::Value> ModuleSystem::LoadModule(const std::string& module_name) {
 void ModuleSystem::OnDidAddPendingModule(
     const std::string& id,
     const std::vector<std::string>& dependencies) {
-  if (!source_map_->Contains(id))
-    return;
+  bool module_system_managed = source_map_->Contains(id);
 
   gin::ModuleRegistry* registry =
       gin::ModuleRegistry::From(context_->v8_context());
   DCHECK(registry);
-  for (std::vector<std::string>::const_iterator it = dependencies.begin();
-       it != dependencies.end();
-       ++it) {
-    if (registry->available_modules().count(*it) == 0)
-      LoadModule(*it);
+  for (const auto& dependency : dependencies) {
+    // If a dependency is not available and either the module being loaded or
+    // the particular dependency is one loaded by ModuleSystem, attempt to load

[not at google - send to devlin, 2015/01/13 21:46:46]

first part is a little hard to parse - I eventually realised it's equivalent to
"if a dependency is not available, and either the module or this dependency is
managed by ModuleSystem, attempt to load it".

[Sam McNally, 2015/01/13 23:48:43]

Done.

+    // it. Ignore other dependencies; the module requesting them should be

[not at google - send to devlin, 2015/01/13 21:46:46]

could you mention what these other dependencies might be?

[Sam McNally, 2015/01/13 23:48:43]

Done.

+    // ensuring that its module's dependencies are available.
+    if (registry->available_modules().count(dependency) == 0 &&
+        (module_system_managed || source_map_->Contains(dependency))) {
+      LoadModule(dependency);
+    }
   }
   registry->AttemptToLoadMoreModules(GetIsolate());
 }