Update to Chromium revision 6e53600d (#386251)

- Remove |accept_lang| parameter from CefJSDialogHandler::OnJSDialog
  and CefFormatUrlForSecurityDisplay (see https://crbug.com/336973#c36).
- Remove remaining NPAPI-related code including functions from
  cef_web_plugin.h (see https://crbug.com/493212#c55).
- Mac: 10.7+ deployment target is now required for client applications.
- Mac: Remove CefBrowserHost::SetWindowVisibility (issue #1375). No
  replacement is required for windowed rendering. Use WasHidden for
  off-screen rendering.
- Windows: Visual Studio 2015 Update 2 is now required when building
  CEF/Chromium.

patch/patches/message_loop_443.patch

@@ -1,8 +1,8 @@
 diff --git message_loop.cc message_loop.cc
-index 04aa9a8..ec302b6 100644
+index 01e7512..e3fcc0d 100644
 --- message_loop.cc
 +++ message_loop.cc
-@@ -139,12 +139,6 @@ MessageLoop::~MessageLoop() {
+@@ -140,12 +140,6 @@ MessageLoop::~MessageLoop() {
    // may be current.
    DCHECK((pump_ && current() == this) || (!pump_ && current() != this));