Convert utility process extension Unpacker IPC to mojo

chrome/utility/extensions/extensions_handler.cc

Index: chrome/utility/extensions/extensions_handler.cc
diff --git a/chrome/utility/extensions/extensions_handler.cc b/chrome/utility/extensions/extensions_handler.cc
index cef009a686baf36881e5f54eedbb5d66c08d12b7..53f871df20aeef35169ba5e3dc398acadcbb3eed 100644
--- a/chrome/utility/extensions/extensions_handler.cc
+++ b/chrome/utility/extensions/extensions_handler.cc
@@ -185,8 +185,7 @@ ExtensionsHandler::ExtensionsHandler() {
   ExtensionsClient::Set(ChromeExtensionsClient::GetInstance());
 }
 
-ExtensionsHandler::~ExtensionsHandler() {
-}
+ExtensionsHandler::~ExtensionsHandler() = default;
 
 // static
 void ExtensionsHandler::PreSandboxStartup() {
@@ -195,10 +194,16 @@ void ExtensionsHandler::PreSandboxStartup() {
 }
 
 // static
+void ExtensionsHandler::UtilityThreadStarted() {
+  UtilityHandler::UtilityThreadStarted();

[Devlin, 2017/02/14 17:24:59]

Why do we need this method, as opposed to calling
UtilityHandler::UtilityThreadStarted() directly?

[Noel Gordon, 2017/02/15 17:28:08]

ExtensionsHandler owns a UtilityHandler utility_handler_, so layering, we let
ExtensionsHandler control it.  And similarly below in
ExtensionsHandler::ExposeInterfacesToBrowser.

[Devlin, 2017/02/17 15:53:56]

I don't quite follow - this is a static method, so ownership in member variables
doesn't really matter.  In ExposeInterfacesToBrowser(), the layering is
important, because it adds extra logic that UtilityHandler doesn't do.  Here, it
just seems to add an extra function call.

+}
+
+// static
 void ExtensionsHandler::ExposeInterfacesToBrowser(
     service_manager::InterfaceRegistry* registry,
     ChromeContentUtilityClient* utility_client,
     bool running_elevated) {
+  UtilityHandler::ExposeInterfacesToBrowser(registry, running_elevated);
   // If our process runs with elevated privileges, only add elevated Mojo
   // services to the interface registry.
   if (running_elevated) {