Accessibility:MAS42A:Menus and context menu are not adapting to high contrast theme

[WiproPSAccTest]

VS Code Version:1.6.1
OS Version:1607

Pre-Requisite:
1.Open visual studio code editor.
2.Using "Ctrl+Shift+P" key Open the command Pallete.
3.Type Theme, Navigate to Preferences: Color Theme and Hit Enter.
4.Navigate to High Contrast and Hit Enter.

Steps to Reproduce:

Scenario 1:
1.Open visual studio code editor.
2.Observe the Menu Bar Visually
Scenario 2:

1. Open visual studio code editor.
2. Hit "Ctrl+Shift+G" to view the Git side bar and Navigate to more button and Hit Enter.
3. Observe the options under More button in High Contrast Theme
   Scenario 3:
4. Open visual studio code editor.
5. Hit "Ctrl+Shift+X" to view the Extensions side bar and Navigate to more button and Hit Enter.
6. Observe the options under More button in High Contrast Theme.

Expected Result:
Scenario 1:
Menu Bar and options under Menu Bar should Adapt the High Contrast Theme of VS Code Editor
Scenario 2:
Icons under More in Git Repository side bar should Adapt the High Contrast Theme of VS Code Editor
Scenario 3:
Icons under More in Extension Repository side bar should Adapt the High Contrast Theme of VS Code Editor.

Actual Result:
Scenario 1:
Issue 1: Menu Bar and options under Menu Bar is not Adapting the High Contrast Theme
Observation: While using OS High Contrast Black Theme, Menu Bar is Partially adapting the OS High Contrast Theme. Issue here is Focused Sub Menu is not Highlighted according to the High Contrast Black Theme
Scenario 2:
Options under More in Git Repository side bar are not Adapting the High Contrast Theme of VS Code Editor
Scenario 3:
Options under More in Extensions side bar are not Adapting the High Contrast Theme of VS Code Editor

User Impact:
Low Vision users will not be able to clearly view the options under Menu Bar as it's not adapting the High Contrast Theme.

[WiproPSAccTest]

Title has been changed to a common format to perform data population.

[bpasero]

We should support this with the new custom menu implementation.

[sbatten]

@bpasero I think we can consider this complete now.