ash: Move VirtualKeyboardStateObserver functionality to ShellObserver

ash/sysui/shell_delegate_mus.cc

Index: ash/sysui/shell_delegate_mus.cc
diff --git a/ash/sysui/shell_delegate_mus.cc b/ash/sysui/shell_delegate_mus.cc
index 8cf896b36b88cd181c747df799be8de66cf0b238..3fe99951f42ac175ddaf0f64c2c8744c67657d8d 100644
--- a/ash/sysui/shell_delegate_mus.cc
+++ b/ash/sysui/shell_delegate_mus.cc
@@ -154,20 +154,6 @@ keyboard::KeyboardUI* ShellDelegateMus::CreateKeyboardUI() {
   return nullptr;
 }
 
-void ShellDelegateMus::VirtualKeyboardActivated(bool activated) {
-  NOTIMPLEMENTED();
-}
-
-void ShellDelegateMus::AddVirtualKeyboardStateObserver(
-    VirtualKeyboardStateObserver* observer) {
-  NOTIMPLEMENTED();
-}
-
-void ShellDelegateMus::RemoveVirtualKeyboardStateObserver(
-    VirtualKeyboardStateObserver* observer) {
-  NOTIMPLEMENTED();
-}
-
 void ShellDelegateMus::OpenUrl(const GURL& url) {
   NOTIMPLEMENTED();
 }