Add support for loading extensions (issue #1947)

- Add CefRequestContext::LoadExtension, CefExtension, CefExtensionHandler and
  related methods/interfaces.
- Add chrome://extensions-support that lists supported Chrome APIs.
- Add CefBrowserHost::SetAutoResizeEnabled and CefDisplayHandler::OnAutoResize
  to support browser resize based on preferred web contents size.
- views: Add support for custom CefMenuButton popups.
- cefclient: Run with `--load-extension=set_page_color` command-line flag for
  an extension loading example. Add `--use-views` on Windows and Linux for an
  even better example.

tests/cefclient/browser/client_handler.cc

@@ -20,6 +20,7 @@
 #include "tests/cefclient/browser/main_context.h"
 #include "tests/cefclient/browser/root_window_manager.h"
 #include "tests/cefclient/browser/test_runner.h"
+#include "tests/shared/browser/extension_util.h"
 #include "tests/shared/browser/resource_util.h"
 #include "tests/shared/common/client_switches.h"
 
@@ -417,6 +418,14 @@ bool ClientHandler::OnConsoleMessage(CefRefPtr<CefBrowser> browser,
   return false;
 }
 
+bool ClientHandler::OnAutoResize(CefRefPtr<CefBrowser> browser,
+                                 const CefSize& new_size) {
+  CEF_REQUIRE_UI_THREAD();
+
+  NotifyAutoResize(new_size);
+  return true;
+}
+
 void ClientHandler::OnBeforeDownload(
     CefRefPtr<CefBrowser> browser,
     CefRefPtr<CefDownloadItem> download_item,
@@ -541,6 +550,19 @@ void ClientHandler::OnAfterCreated(CefRefPtr<CefBrowser> browser) {
   if (mouse_cursor_change_disabled_)
     browser->GetHost()->SetMouseCursorChangeDisabled(true);
 
+  if (browser->GetHost()->GetExtension()) {
+    // Browsers hosting extension apps should auto-resize.
+    browser->GetHost()->SetAutoResizeEnabled(true, CefSize(20, 20),
+                                             CefSize(1000, 1000));
+
+    CefRefPtr<CefExtension> extension = browser->GetHost()->GetExtension();
+    if (extension_util::IsInternalExtension(extension->GetPath())) {
+      // Register the internal handler for extension resources.
+      extension_util::AddInternalExtensionToResourceManager(extension,
+                                                            resource_manager_);
+    }
+  }
+
   NotifyBrowserCreated(browser);
 }
 
@@ -623,8 +645,11 @@ bool ClientHandler::OnOpenURLFromTab(
       target_disposition == WOD_NEW_FOREGROUND_TAB) {
     // Handle middle-click and ctrl + left-click by opening the URL in a new
     // browser window.
-    MainContext::Get()->GetRootWindowManager()->CreateRootWindow(
-        true, is_osr(), CefRect(), target_url);
+    RootWindowConfig config;
+    config.with_controls = true;
+    config.with_osr = is_osr();
+    config.url = target_url;
+    MainContext::Get()->GetRootWindowManager()->CreateRootWindow(config);
     return true;
   }
 
@@ -867,9 +892,11 @@ void ClientHandler::ShowSSLInformation(CefRefPtr<CefBrowser> browser) {
 
   ss << "</body></html>";
 
-  MainContext::Get()->GetRootWindowManager()->CreateRootWindow(
-      false, is_osr(), CefRect(),
-      test_runner::GetDataURI(ss.str(), "text/html"));
+  RootWindowConfig config;
+  config.with_controls = false;
+  config.with_osr = is_osr();
+  config.url = test_runner::GetDataURI(ss.str(), "text/html");
+  MainContext::Get()->GetRootWindowManager()->CreateRootWindow(config);
 }
 
 bool ClientHandler::CreatePopupWindow(CefRefPtr<CefBrowser> browser,
@@ -969,6 +996,18 @@ void ClientHandler::NotifyFullscreen(bool fullscreen) {
     delegate_->OnSetFullscreen(fullscreen);
 }
 
+void ClientHandler::NotifyAutoResize(const CefSize& new_size) {
+  if (!CURRENTLY_ON_MAIN_THREAD()) {
+    // Execute this method on the main thread.
+    MAIN_POST_CLOSURE(
+        base::Bind(&ClientHandler::NotifyAutoResize, this, new_size));
+    return;
+  }
+
+  if (delegate_)
+    delegate_->OnAutoResize(new_size);
+}
+
 void ClientHandler::NotifyLoadingState(bool isLoading,
                                        bool canGoBack,
                                        bool canGoForward) {