Add new constructors for all DesktopFrame inheritances

This change adds constructors for all DesktopFrame inheritances to pass in
DesktopRect instead of DesktopSize.
Because the newly added constructors and DesktopFrame::top_left() function are
not actively used, this change should have no logic impact.

Bug: webrtc:7950
Change-Id: If78187865c991211dfc28d3723403ce6e6fe0290
Reviewed-on: https://chromium-review.googlesource.com/590508
Reviewed-by: Jamie Walch <jamiewalch@chromium.org>
Commit-Queue: Zijie He <zijiehe@chromium.org>
Cr-Commit-Position: refs/heads/master@{#19204}

webrtc/modules/desktop_capture/shared_desktop_frame.cc

@@ -47,7 +47,7 @@ bool SharedDesktopFrame::IsShared() {
 }
 
 SharedDesktopFrame::SharedDesktopFrame(rtc::scoped_refptr<Core> core)
-    : DesktopFrame((*core)->size(),
+    : DesktopFrame((*core)->rect(),
                    (*core)->stride(),
                    (*core)->data(),
                    (*core)->shared_memory()),