extensions: Register 'app' and 'webstore' bindings only if they are available.

extensions/renderer/dispatcher.cc

 // Copyright 2014 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 "extensions/renderer/dispatcher.h"
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/command_line.h"
 #include "base/debug/alias.h"
@@ skipping 985 matching lines @@
   v8::Context::Scope context_scope(context->v8_context());
 
   // TODO(kalman): Make the bindings registration have zero overhead then run
   // the same code regardless of context type.
   switch (context->context_type()) {
     case Feature::UNSPECIFIED_CONTEXT:
     case Feature::WEB_PAGE_CONTEXT:
     case Feature::BLESSED_WEB_PAGE_CONTEXT: {
       // Web page context; it's too expensive to run the full bindings code.
       // Hard-code that the app and webstore APIs are available...
-      RegisterBinding("app", context);
-      RegisterBinding("webstore", context);
+      if (IsApiAvailable(std::string("app"), context))

[not at google - send to devlin, 2014/08/05 22:43:39]

it's easier to do

if (context->GetAvailability("app").is_available())
  ...

and below.

[sadrul, 2014/08/05 22:51:02]

Nice! Done.

+        RegisterBinding("app", context);
+
+      if (IsApiAvailable(std::string("webstore"), context))

[not at google - send to devlin, 2014/08/05 22:43:39]

also, no need to explicitly construct a std::string here.

[sadrul, 2014/08/05 22:51:02]

Acknowledged.

+          RegisterBinding("webstore", context);

[not at google - send to devlin, 2014/08/05 22:43:39]

indentation

[sadrul, 2014/08/05 22:51:02]

Done.

 
       // ... and that the runtime API might be available if any extension can
       // connect to it.
       bool runtime_is_available = false;
       for (ExtensionSet::const_iterator it = extensions_.begin();
            it != extensions_.end();
            ++it) {
         ExternallyConnectableInfo* info =
             static_cast<ExternallyConnectableInfo*>(
                 (*it)->GetManifestData(manifest_keys::kExternallyConnectable));
@@ skipping 141 matching lines @@
 bool Dispatcher::IsSandboxedPage(const GURL& url) const {
   if (url.SchemeIs(kExtensionScheme)) {
     const Extension* extension = extensions_.GetByID(url.host());
     if (extension) {
       return SandboxedPageInfo::IsSandboxedPage(extension, url.path());
     }
   }
   return false;
 }
 
+bool Dispatcher::IsApiAvailable(const std::string& api_name,
+                                ScriptContext* context) {
+  return ExtensionAPI::GetSharedInstance()->IsAvailable(
+              api_name, context->extension(), context->context_type(),
+              context->GetURL()).is_available();
+}
+
 Feature::Context Dispatcher::ClassifyJavaScriptContext(
     const Extension* extension,
     int extension_group,
     const GURL& url,
     const blink::WebSecurityOrigin& origin) {
   DCHECK_GE(extension_group, 0);
   if (extension_group == EXTENSION_GROUP_CONTENT_SCRIPTS) {
     return extension ?  // TODO(kalman): when does this happen?
                Feature::CONTENT_SCRIPT_CONTEXT
                      : Feature::UNSPECIFIED_CONTEXT;
@@ skipping 106 matching lines @@
     return v8::Handle<v8::Object>();
 
   if (bind_name)
     *bind_name = split.back();
 
   return bind_object.IsEmpty() ? AsObjectOrEmpty(GetOrCreateChrome(context))
                                : bind_object;
 }
 
 }  // namespace extensions