Make app_custom_bindings.js lazily evaluated so it doesn't execute on every page load.

chrome/renderer/extensions/extension_dispatcher.cc

Index: chrome/renderer/extensions/extension_dispatcher.cc
diff --git a/chrome/renderer/extensions/extension_dispatcher.cc b/chrome/renderer/extensions/extension_dispatcher.cc
index 1833d64cfa85c23499ccefccec4af4b16bba2fd4..84e41a0ca7d4d0342c9646021ee63dd7cde2f226 100644
--- a/chrome/renderer/extensions/extension_dispatcher.cc
+++ b/chrome/renderer/extensions/extension_dispatcher.cc
@@ -118,6 +118,24 @@ class PrintNativeHandler : public NativeHandler {
   }
 };
 
+void InstallAppBindings(ModuleSystem* module_system,
+                        v8::Handle<v8::Object> chrome,
+                        v8::Handle<v8::Object> chrome_hidden) {
+  module_system->SetLazyField(chrome, "app", "app", "chromeApp");
+  module_system->SetLazyField(chrome, "appNotifications", "app",

[not at google - send to devlin, 2012/03/25 22:42:58]

add TODO to pull appNotifications out into its own lazy field?

[koz (OOO until 15th September), 2012/03/26 01:36:09]

The 'app' module has variables in it that are shared between
chrome.appNotifications and chromeHidden.app, so they need to come from the same
module.

[not at google - send to devlin, 2012/03/26 02:29:49]

I don't think they do really; rather I think that stuff is incorrectly on
chromeHidden.app when it should be on chromeHidden.appNotifications.

[koz (OOO until 15th September), 2012/03/26 03:58:59]

Ah, true. Though looking at the code I see that there's already a TODO for you
to split that out into its own module (which implies it will have its own lazy
field).

+                              "chromeAppNotifications");
+  module_system->SetLazyField(chrome_hidden, "app", "app",
+                              "chromeHiddenApp");
+}
+
+void InstallWebstoreBindings(ModuleSystem* module_system,
+                             v8::Handle<v8::Object> chrome,
+                             v8::Handle<v8::Object> chrome_hidden) {
+  module_system->SetLazyField(chrome, "webstore", "webstore", "chromeWebstore");
+  module_system->SetLazyField(chrome_hidden, "webstore", "webstore",
+                              "chromeHiddenWebstore");
+}

[not at google - send to devlin, 2012/03/25 22:42:58]

I guess this isn't scalable to arbitrary APIs.

Not worth worrying about this now since any further optimisation would only
apply to extensions -- which have a high likelihood of using APIs which they
request permission for (with the exception of automatically-granted APIs, so
maybe somewhat useful).

I guess we can just handwrite any further APIs opened up to all webpages here,
but it would be nice to have a mechanism arbitrarily able to be generated.

Probably worth noting that or adding a TODO?

[koz (OOO until 15th September), 2012/03/26 01:36:09]

You mean being able to make arbitrary modules lazy without having custom code
like this? It could be possible with a convention, but that seems like more
magic than its worth.

[not at google - send to devlin, 2012/03/26 02:29:49]

Yeah agreed.

+
 }
 
 ExtensionDispatcher::ExtensionDispatcher()
@@ -471,6 +489,10 @@ void ExtensionDispatcher::DidCreateScriptContext(
   if (extension)
     manifest_version = extension->manifest_version();
 

[not at google - send to devlin, 2012/03/25 22:42:58]

could just have the typedef here?

[koz (OOO until 15th September), 2012/03/26 01:36:09]

Done.

+  std::map<std::string, BindingInstaller> optimized_bindings;
+  optimized_bindings["app"] = InstallAppBindings;
+  optimized_bindings["webstore"] = InstallWebstoreBindings;

[not at google - send to devlin, 2012/03/25 22:42:58]

lazy_bindings?

[koz (OOO until 15th September), 2012/03/26 01:36:09]

Nice. Done.

+
   // Create the 'chrome' variable if it doesn't already exist.
   {
     v8::HandleScope handle_scope;
@@ -513,6 +535,15 @@ void ExtensionDispatcher::DidCreateScriptContext(
 
   for (std::set<std::string>::iterator i = apis->begin(); i != apis->end();
       ++i) {
+    if (optimized_bindings.count(*i) > 0) {

[not at google - send to devlin, 2012/03/25 22:42:58]

nit: use find() here, ->second below.

[koz (OOO until 15th September), 2012/03/26 01:36:09]

Done.

+      v8::Handle<v8::Object> global(v8::Context::GetCurrent()->Global());
+      v8::Handle<v8::Object> chrome =
+          global->Get(v8::String::New("chrome"))->ToObject();

[not at google - send to devlin, 2012/03/25 22:42:58]

re-use the reference to "chrome" from the one created above? (line 501)

[koz (OOO until 15th September), 2012/03/26 01:36:09]

I think better to not. This method is already way too long so better to have
each part as modular as possible.

+      v8::Handle<v8::Object> chrome_hidden =
+          ChromeV8Context::GetOrCreateChromeHidden(v8_context)->ToObject();
+      optimized_bindings[*i](module_system.get(), chrome, chrome_hidden);
+      continue;
+    }

[not at google - send to devlin, 2012/03/25 22:42:58]

nit: else not continue

[koz (OOO until 15th September), 2012/03/26 01:36:09]

Done.

     module_system->Require(*i);
   }