Prevent chrome.app JSON schema from loading on every page

chrome/renderer/extensions/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/dispatcher.h"
 
 #include "base/callback.h"
 #include "base/command_line.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/string_piece.h"
@@ skipping 636 matching lines @@
                                       int world_id) {
   g_hack_extension_group = extension_group;
   return true;
 }
 
 v8::Handle<v8::Object> Dispatcher::GetOrCreateObject(
     v8::Handle<v8::Object> object,
     const std::string& field) {
   v8::HandleScope handle_scope;
   v8::Handle<v8::String> key = v8::String::New(field.c_str());
-  // This little dance is for APIs that may be unavailable but have available
-  // children. For example, chrome.app can be unavailable, while
-  // chrome.app.runtime is available. The lazy getter for chrome.app must be
-  // deleted, so that there isn't an error when accessing chrome.app.runtime.
-  if (object->Has(key)) {
+  // If the object has a callback property, it is assumed it is an unavailable
+  // API, so it is safe to delete. This is checked before GetOrCreateObject is
+  // called.
+  if (object->HasRealNamedCallbackProperty(key)) {
+    object->Delete(key);
+  } else if (object->HasRealNamedProperty(key)) {
     v8::Handle<v8::Value> value = object->Get(key);
-    if (value->IsObject())
-      return handle_scope.Close(v8::Handle<v8::Object>::Cast(value));
-    else
-      object->Delete(key);
+    CHECK(value->IsObject());
+    return handle_scope.Close(v8::Handle<v8::Object>::Cast(value));
   }
 
   v8::Handle<v8::Object> new_object = v8::Object::New();
   object->Set(key, new_object);
   return handle_scope.Close(new_object);
 }
 
 void Dispatcher::RegisterSchemaGeneratedBindings(
     ModuleSystem* module_system,
-    ChromeV8Context* context,
-    v8::Handle<v8::Context> v8_context) {
+    ChromeV8Context* context) {
   std::set<std::string> apis =
       ExtensionAPI::GetSharedInstance()->GetAllAPINames();
   for (std::set<std::string>::iterator it = apis.begin();
        it != apis.end(); ++it) {
     const std::string& api_name = *it;
 
     Feature* feature =
         BaseFeatureProvider::GetAPIFeatures()->GetFeature(api_name);
     if (feature && feature->IsInternal())
       continue;
 
     std::vector<std::string> split;
     base::SplitString(api_name, '.', &split);
 
-    v8::Handle<v8::Object> bind_object = GetOrCreateChrome(v8_context);
-    for (size_t i = 0; i < split.size() - 1; ++i)
+    v8::Handle<v8::Object> bind_object =
+        GetOrCreateChrome(context->v8_context());
+    std::string current_name;

[not at google - send to devlin, 2013/04/04 01:30:26]

ok... I think I understand what you're doing here. If an API has a parent, check
its availability and all its parents' availability. If the parent is available
and it isn't, don't install the bindings, but leave the object there.

Maybe you could explain something along those lines in the comment. It's pretty
subtle. And give the canonical example (apps) - well actually that's the only
example right?

[cduvall, 2013/04/11 00:02:56]

Done.

+    bool only_parent_available = false;

[not at google - send to devlin, 2013/04/04 01:30:26]

only_ancestor_available?

[cduvall, 2013/04/11 00:02:56]

Done.

+    for (size_t i = 0; i < split.size() - 1; ++i) {
+      current_name += (i ? ".": "") + split[i];

[not at google - send to devlin, 2013/04/04 01:30:26]

ancestor_name?

[cduvall, 2013/04/11 00:02:56]

Done.

+      if (!current_name.empty() &&
+          context->GetAvailability(current_name).is_available() &&
+          !context->GetAvailability(api_name).is_available()) {
+        only_parent_available = true;
+        break;
+      }
       bind_object = GetOrCreateObject(bind_object, split[i]);
+    }
+    if (only_parent_available)
+      continue;
 
     if (lazy_bindings_map_.find(api_name) != lazy_bindings_map_.end()) {
-      InstallBindings(module_system, v8_context, api_name);
+      InstallBindings(module_system, context->v8_context(), api_name);
     } else if (!source_map_.Contains(api_name)) {
       module_system->RegisterNativeHandler(
           api_name,
           scoped_ptr<NativeHandler>(new BindingGeneratingNativeHandler(
               module_system,
               api_name,
               "binding")));
       module_system->SetNativeLazyField(bind_object,
                                         split.back(),
                                         api_name,
@@ skipping 268 matching lines @@
        BackgroundInfo::HasLazyBackgroundPage(extension));
   module_system->RegisterNativeHandler("process",
       scoped_ptr<NativeHandler>(new ProcessInfoNativeHandler(
           this, v8_context, context->GetExtensionID(),
           context->GetContextTypeDescription(),
           ChromeRenderProcessObserver::is_incognito_process(),
           manifest_version, send_request_disabled)));
 
   GetOrCreateChrome(v8_context);
 
-  // Loading JavaScript is expensive, so only run the full API bindings
-  // generation mechanisms in extension pages (NOT all web pages).
-  switch (context_type) {
-    case Feature::UNSPECIFIED_CONTEXT:
-    case Feature::WEB_PAGE_CONTEXT:
-      // TODO(kalman): see comment below about ExtensionAPI.
-      InstallBindings(module_system.get(), v8_context, "app");
-      InstallBindings(module_system.get(), v8_context, "webstore");
-      break;
-    case Feature::BLESSED_EXTENSION_CONTEXT:
-    case Feature::UNBLESSED_EXTENSION_CONTEXT:
-    case Feature::CONTENT_SCRIPT_CONTEXT:
-      if (extension && !extension->is_platform_app())
-        module_system->Require("miscellaneous_bindings");
-      module_system->Require("json");  // see paranoid comment in json.js
+  // TODO(kalman): see comment below about ExtensionAPI.
+  InstallBindings(module_system.get(), v8_context, "app");
+  InstallBindings(module_system.get(), v8_context, "webstore");
+  if (extension && !extension->is_platform_app())
+    module_system->Require("miscellaneous_bindings");
+  module_system->Require("json");  // see paranoid comment in json.js
 
-      // TODO(kalman): move this code back out of the switch and execute it
-      // regardless of |context_type|. ExtensionAPI knows how to return the
-      // correct APIs, however, until it doesn't have a 2MB overhead we can't
-      // load it in every process.
-      RegisterSchemaGeneratedBindings(module_system.get(),
-                                      context,
-                                      v8_context);
-      break;
-  }
+  RegisterSchemaGeneratedBindings(module_system.get(), context);
 
   bool is_within_platform_app = IsWithinPlatformApp(frame);
   // Inject custom JS into the platform app context.
   if (is_within_platform_app)
     module_system->Require("platformApp");
 
   // Only platform apps support the <webview> tag, because the "webView" and
   // "denyWebView" modules will affect the performance of DOM modifications
   // (http://crbug.com/196453).
   if (context_type == Feature::BLESSED_EXTENSION_CONTEXT &&
@@ skipping 353 matching lines @@
     std::string error_msg = base::StringPrintf(kMessage, function_name.c_str());
     v8::ThrowException(
         v8::Exception::Error(v8::String::New(error_msg.c_str())));
     return false;
   }
 
   return true;
 }
 
 }  // namespace extensions