I want use chrome or chromium application ass dekstop application. I wrote custom .desktop file to start web application.
Example .desktop:
---------------
#!/usr/bin/env xdg-open
[Desktop Entry]
Categories=Internet
Version=1.0
Terminal=false
Type=Application
Name=Gmail
Exec=/opt/google/chrome/google-chrome --profile-directory=Default --app-id=pjkljhegncpnkpknbcohdijeoejaedia
Icon=chrome-pjkljhegncpnkpknbcohdijeoejaedia-Default
StartupWMClass=crx_pjkljhegncpnkpknbcohdijeoejaedia
-------------------
or another:
-------------------
[Desktop Entry]
Categories=Internet
Comment[ru_RU]=WhatsApp Client
Comment=WhatsApp Client
Exec=whatsapp --icon=/usr/share/icons/elementary-plus/apps/128/chrome-https___web.whatsapp.com_.svg
GenericName[ru_RU]=WhatsApp Client
GenericName=WhatsApp Client
Icon=/usr/share/icons/elementary-plus/apps/128/chrome-https___web.whatsapp.com_.svg
MimeType=
Name[ru_RU]=WhatsApp
Name=WhatsApp
NoDisplay=false
Path[$e]=
StartupNotify=false
StartupWMClass=WhatsApp
Terminal=0
TerminalOptions=
Type=Application
X-DBUS-ServiceName=
X-DBUS-StartupType=
X-KDE-SubstituteUID=false
X-KDE-Username=
X-KDE-StartupNotify=false
---------------------

But when I start application I see in taskbar chromium icon, not webapp icon(

Reproducible: Always

Steps to Reproduce:
1. Creat custom app launcher with chromium 
2. Start this application
3. See taskbar

Actual Results:  
In taskbar appliaction icon is taken from Exec= variable

Expected Results:  
Application icon is taken from Icon= variable
Example: http://i.stack.imgur.com/yqsH6.png