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.

libcef_dll/cpptoc/get_extension_resource_callback_cpptoc.cc

@@ -0,0 +1,82 @@
+// Copyright (c) 2017 The Chromium Embedded Framework Authors. All rights
+// reserved. Use of this source code is governed by a BSD-style license that
+// can be found in the LICENSE file.
+//
+// ---------------------------------------------------------------------------
+//
+// This file was generated by the CEF translator tool. If making changes by
+// hand only do so within the body of existing method and function
+// implementations. See the translator.README.txt file in the tools directory
+// for more information.
+//
+// $hash=a14686b53e028382d8dc537009d7a18263f753d6$
+//
+
+#include "libcef_dll/cpptoc/get_extension_resource_callback_cpptoc.h"
+#include "libcef_dll/cpptoc/stream_reader_cpptoc.h"
+
+namespace {
+
+// MEMBER FUNCTIONS - Body may be edited by hand.
+
+void CEF_CALLBACK get_extension_resource_callback_cont(
+    struct _cef_get_extension_resource_callback_t* self,
+    struct _cef_stream_reader_t* stream) {
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  DCHECK(self);
+  if (!self)
+    return;
+  // Unverified params: stream
+
+  // Execute
+  CefGetExtensionResourceCallbackCppToC::Get(self)->Continue(
+      CefStreamReaderCppToC::Unwrap(stream));
+}
+
+void CEF_CALLBACK get_extension_resource_callback_cancel(
+    struct _cef_get_extension_resource_callback_t* self) {
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  DCHECK(self);
+  if (!self)
+    return;
+
+  // Execute
+  CefGetExtensionResourceCallbackCppToC::Get(self)->Cancel();
+}
+
+}  // namespace
+
+// CONSTRUCTOR - Do not edit by hand.
+
+CefGetExtensionResourceCallbackCppToC::CefGetExtensionResourceCallbackCppToC() {
+  GetStruct()->cont = get_extension_resource_callback_cont;
+  GetStruct()->cancel = get_extension_resource_callback_cancel;
+}
+
+template <>
+CefRefPtr<CefGetExtensionResourceCallback>
+CefCppToCRefCounted<CefGetExtensionResourceCallbackCppToC,
+                    CefGetExtensionResourceCallback,
+                    cef_get_extension_resource_callback_t>::
+    UnwrapDerived(CefWrapperType type,
+                  cef_get_extension_resource_callback_t* s) {
+  NOTREACHED() << "Unexpected class type: " << type;
+  return NULL;
+}
+
+#if DCHECK_IS_ON()
+template <>
+base::AtomicRefCount CefCppToCRefCounted<
+    CefGetExtensionResourceCallbackCppToC,
+    CefGetExtensionResourceCallback,
+    cef_get_extension_resource_callback_t>::DebugObjCt ATOMIC_DECLARATION;
+#endif
+
+template <>
+CefWrapperType
+    CefCppToCRefCounted<CefGetExtensionResourceCallbackCppToC,
+                        CefGetExtensionResourceCallback,
+                        cef_get_extension_resource_callback_t>::kWrapperType =
+        WT_GET_EXTENSION_RESOURCE_CALLBACK;