Implementing TabManager extensions API Discard Function.

chrome/browser/extensions/api/tabs/tabs_api.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/browser/extensions/api/tabs/tabs_api.h"
 
 #include <stddef.h>
 #include <algorithm>
 #include <limits>
 #include <memory>
@@ skipping 2150 matching lines @@
   api::tabs::ZoomSettings zoom_settings;
   ZoomModeToZoomSettings(zoom_mode, &zoom_settings);
   zoom_settings.default_zoom_factor.reset(new double(
       content::ZoomLevelToZoomFactor(zoom_controller->GetDefaultZoomLevel())));
 
   results_ = api::tabs::GetZoomSettings::Results::Create(zoom_settings);
   SendResponse(true);
   return true;
 }
 
+bool TabsDiscardFunction::RunSync() {
+  std::unique_ptr<tabs::Discard::Params> params(
+      tabs::Discard::Params::Create(*args_));
+  EXTENSION_FUNCTION_VALIDATE(params);
+
+  WebContents* contents = nullptr;
+  // If |tab_id| is given, find the web_contents respective to it.
+  // Otherwise invoke discard function in TabManager with null web_contents
+  // that will discard the least important tab.
+  if (params->tab_id) {
+    int tab_id = *params->tab_id;
+    if (!GetTabById(tab_id, GetProfile(), include_incognito(), nullptr, nullptr,
+                    &contents, nullptr, &error_)) {
+      return false;
+    }
+  }
+  // Discard the tab.
+  memory::TabManager* tab_manager = g_browser_process->GetTabManager();
+  if (!tab_manager)

[Devlin, 2016/07/19 22:49:12]

When can this be null?

[Anderson Silva, 2016/07/20 16:24:01]

It's null on non-supported platforms (Android, iOS). But as extensions are not
supported on those, we can remove this.

+    return false;
+  contents = tab_manager->DiscardTabByExtension(contents);
+
+  if (!has_callback())

[Devlin, 2016/07/19 22:49:11]

I understand the motivation for this, but if/when we move to promise-based apis,
this will make the transition harder.  Let's just create the result in all
cases.  Extensions shouldn't be calling discard very frequently.

[Anderson Silva, 2016/07/20 16:24:01]

Done.

+    return true;
+
+  // Create result to be returned if callback is present.
+  // We have to return a Tab object and the success boolean, so create a
+  // default object and replace it with the real tab in case of success
+  // (contents is not null).
+  bool success = !!contents;
+  std::unique_ptr<api::tabs::Tab> tab(new api::tabs::Tab);
+  if (success)
+    tab = ExtensionTabUtil::CreateTabObject(contents);
+  results_ = api::tabs::Discard::Results::Create(*tab, success);
+  return true;
+}
+
 }  // namespace extensions