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

chrome/renderer/extensions/extension_dispatcher.cc

 // Copyright (c) 2012 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.
 
 #include "chrome/renderer/extensions/extension_dispatcher.h"
 
 #include "base/callback.h"
 #include "base/command_line.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/string_piece.h"
@@ skipping 100 matching lines @@
 
     std::vector<std::string> components;
     for (int i = 0; i < args.Length(); ++i)
       components.push_back(*v8::String::Utf8Value(args[i]->ToString()));
 
     LOG(ERROR) << JoinString(components, ',');
     return v8::Undefined();
   }
 };
 
+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()
     : is_webkit_initialized_(false),
       webrequest_adblock_(false),
       webrequest_adblock_plus_(false),
       webrequest_other_(false),
       source_map_(&ResourceBundle::GetSharedInstance()) {
   const CommandLine& command_line = *(CommandLine::ForCurrentProcess());
   is_extension_process_ =
@@ skipping 332 matching lines @@
   RegisterNativeHandlers(module_system.get(), context);
 
   module_system->RegisterNativeHandler("chrome_hidden",
       scoped_ptr<NativeHandler>(new ChromeHiddenNativeHandler()));
   module_system->RegisterNativeHandler("print",
       scoped_ptr<NativeHandler>(new PrintNativeHandler()));
 
   int manifest_version = 1;
   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;
     v8::Handle<v8::String> chrome_string(v8::String::New("chrome"));
     v8::Handle<v8::Object> global(v8::Context::GetCurrent()->Global());
     if (global->Get(chrome_string)->IsUndefined())
       global->Set(chrome_string, v8::Object::New());
   }
 
   // Loading JavaScript is expensive, so only run the full API bindings
@@ skipping 22 matching lines @@
   // to write. We really need to factor things differently to delete the
   // concept of a test extension ID.
   if (IsTestExtensionId(extension_id)) {
     module_system->Require("miscellaneous_bindings");
     module_system->Require("schema_generated_bindings");
     apis->insert("extension");
   }
 
   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);
   }
 
   module_system->set_natives_enabled(false);
 
   context->set_module_system(module_system.Pass());
 
   context->DispatchOnLoadEvent(
       is_extension_process_,
       ChromeRenderProcessObserver::is_incognito_process(),
@@ skipping 176 matching lines @@
     return Feature::BLESSED_EXTENSION_CONTEXT;
 
   if (extensions_.ExtensionBindingsAllowed(url_info))
     return Feature::UNBLESSED_EXTENSION_CONTEXT;
 
   if (url_info.url().is_valid())
     return Feature::WEB_PAGE_CONTEXT;
 
   return Feature::UNSPECIFIED_CONTEXT;
 }