Fix handling of failure case of IsWindowOnCurrentVirtualDesktop

If the IVirtualDestkopManager COM method IsWindowOnCurrentVirtualDesktop
fails on a window, treat the window as non-occluding, because that's
safer than treating it as occluding - it might be on an another virtual
desktop, and thus should be non-occluding.

Previously, IsWindowOnCurrentVirtualDesktop was incorrectly returning
base::Optional nullopt on Windows 7 and 8.1 (i.e., unknown). This CL
makes it return true, because there are no virtual desktops on Win 7/8,
so every window is on the current desktop. This allows us to require
that IsWindowOnCurrentVirtualDesktop return true to say that a window
is occluding - previously we checked for != false, to handle Win7.

Bug: 813093
Change-Id: Iee49eff9333a8530314720702b1815256acdbfc5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2410420Reviewed-by: Jesse McKenna <jessemckenna@google.com>
Commit-Queue: David Bienvenu <davidbienvenu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#806683}

ui/aura/native_window_occlusion_tracker_win.cc

@@ -4,6 +4,7 @@
 
 #include "ui/aura/native_window_occlusion_tracker_win.h"
 
+#include <dwmapi.h>
 #include <memory>
 
 #include "base/bind.h"
@@ -19,8 +20,6 @@
 #include "base/win/windows_version.h"
 #include "ui/aura/window_tree_host.h"
 
-#include "dwmapi.h"
-
 namespace aura {
 
 namespace {
@@ -669,18 +668,18 @@ bool NativeWindowOcclusionTrackerWin::WindowOcclusionCalculator::
         HWND hwnd,
         gfx::Rect* window_rect) {
   return IsWindowVisibleAndFullyOpaque(hwnd, window_rect) &&
-         (IsWindowOnCurrentVirtualDesktop(hwnd) != false);
+         (IsWindowOnCurrentVirtualDesktop(hwnd) == true);
 }
 
 base::Optional<bool> NativeWindowOcclusionTrackerWin::
     WindowOcclusionCalculator::IsWindowOnCurrentVirtualDesktop(HWND hwnd) {
-  if (virtual_desktop_manager_) {
-    BOOL on_current_desktop;
+  if (!virtual_desktop_manager_)
+    return true;
 
-    if (SUCCEEDED(virtual_desktop_manager_->IsWindowOnCurrentVirtualDesktop(
-            hwnd, &on_current_desktop))) {
-      return on_current_desktop;
-    }
+  BOOL on_current_desktop;
+  if (SUCCEEDED(virtual_desktop_manager_->IsWindowOnCurrentVirtualDesktop(
+          hwnd, &on_current_desktop))) {
+    return on_current_desktop;
   }
   return base::nullopt;
 }