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/browser_plugin_guest_1565.patch

@@ -1,5 +1,5 @@
 diff --git browser/browser_plugin/browser_plugin_guest.cc browser/browser_plugin/browser_plugin_guest.cc
-index 007c977..069e8d4 100644
+index ad4474f..d0318065 100644
 --- browser/browser_plugin/browser_plugin_guest.cc
 +++ browser/browser_plugin/browser_plugin_guest.cc
 @@ -28,7 +28,7 @@
@@ -36,7 +36,7 @@ index 007c977..069e8d4 100644
    }
  
    RendererPreferences* renderer_prefs =
-@@ -754,11 +753,10 @@ void BrowserPluginGuest::OnWillAttachComplete(
+@@ -749,11 +748,10 @@ void BrowserPluginGuest::OnWillAttachComplete(
          ->GetWidget()
          ->Init();
      GetWebContents()->GetMainFrame()->Init();