Content changes are not reflected in content perspective

[issue moved from CHANNELMGR project, find original description below]

When a document was opened in the content perspective, and then its content gets changed in another perspective (Channel Manager, Visual Editing), these changes are not visible when returning to the content perspective. To provide a better UX when switching between perspectives, these changes should be loaded into the open documents when returning to the content perspective.

[original description:]

Tested on HAP VE-psp1 branch.

Scenario:
1, Go to content perspective of some news document,
2. Start edit document. Do not save.
3. Go to Channels perspective.
4. Open same News document to edit it in right side panel.

Expected behavior: New changes should be available to edit in right side panel.
Current behavior: There is no changes available to edit in right side panel.