[EXPLORER] Use STDMETHODIMP and override (#7645)

Follow the standard way.
JIRA issue: CORE-19469
- Use STDMETHODIMP and override keyword
  instead of virtual HRESULT STDMETHODCALLTYPE.
- Delete CTaskBand::ProcessMessage and
  CTaskBand::ContainsWindow methods.
  I think they are useless.

base/shell/explorer/trayntfy.cpp

@@ -496,7 +496,10 @@ public:
         return GetParent().SendMessage(WM_NOTIFY, 0, (LPARAM)hdr);
     }
 
-    HRESULT WINAPI GetWindow(HWND* phwnd)
+    // *** IOleWindow methods ***
+
+    STDMETHODIMP
+    GetWindow(HWND* phwnd) override
     {
         if (!phwnd)
             return E_INVALIDARG;
@@ -504,7 +507,8 @@ public:
         return S_OK;
     }
 
-    HRESULT WINAPI ContextSensitiveHelp(BOOL fEnterMode)
+    STDMETHODIMP
+    ContextSensitiveHelp(BOOL fEnterMode) override
     {
         return E_NOTIMPL;
     }