Refuse to show Alt+Tab UI concurrently with virtual keyboard.

chrome/browser/extensions/api/virtual_keyboard_private/chrome_virtual_keyboard_delegate.cc

Index: chrome/browser/extensions/api/virtual_keyboard_private/chrome_virtual_keyboard_delegate.cc
diff --git a/chrome/browser/extensions/api/virtual_keyboard_private/chrome_virtual_keyboard_delegate.cc b/chrome/browser/extensions/api/virtual_keyboard_private/chrome_virtual_keyboard_delegate.cc
index 27a148087557b45ce77138f9a9edb031b2de368b..3e4b554fb7b49222300b5c7f925e3811ed3cfcae 100644
--- a/chrome/browser/extensions/api/virtual_keyboard_private/chrome_virtual_keyboard_delegate.cc
+++ b/chrome/browser/extensions/api/virtual_keyboard_private/chrome_virtual_keyboard_delegate.cc
@@ -155,7 +155,7 @@ bool ChromeVirtualKeyboardDelegate::SendKeyEvent(const std::string& type,
                                           char_value,
                                           key_code,
                                           key_name,
-                                          modifiers,
+                                          modifiers & ui::EF_IS_SYNTHESIZED,

[Shu Chen, 2016/08/23 02:56:58]

You need to do the same thing in here: 
https://cs.chromium.org/chromium/src/chrome/browser/chromeos/input_method/inp....

[Evan Stade, 2016/08/23 03:38:21]

thanks, done in InputMethodEngineBase::SendKeyEvents. I don't know how to verify
this is correct though.

                                           window->GetHost());
 }