[Window Capture] Mouse cursor missing during window sharing on Mac OSX

CGWindowID is 32-bit, WindowId is 64-bit, using WindowId to receive int value
from CFNumberGetValue() causes the top 32 bits to be random. WindowFinderMac is
impacted by this issue and returns a random number. WindowCapturerMac cannot
match the window_id_ with the the random number.

Meanwhile MouseCursorMonitorMac uses window title to match "Dock" window. See,
https://cs.chromium.org/chromium/src/third_party/webrtc/modules/desktop_capture/mouse_cursor_monitor_mac.mm?rcl=a194e58e799ccab6c999998e5d0f75725aa3f748&l=174

This logic should not be necessary on 10.12 or upper, the name of dock window
is not "Dock" anymore. But to ensure the consistency on old platforms, I have
also added this logic back into GetWindowList() function.

Bug: chromium:778049
Change-Id: Ie827bcd5d31f2ca69ff24c24cf640cb7cc50d419
Reviewed-on: https://webrtc-review.googlesource.com/15782
Commit-Queue: Zijie He <[email protected]>
Reviewed-by: Jamie Walch <[email protected]>
Cr-Commit-Position: refs/heads/master@{#20451}

modules/desktop_capture/mac/window_list_utils.cc

@@ -96,6 +96,12 @@ bool GetWindowList(rtc::FunctionView<bool(CFDictionaryRef)> on_window,
       continue;
     }
 
+    // TODO(webrtc:8460): On 10.12, the name of the dock window is not "Dock"
+    // anymore. The following check should be removed soon or later.
+    if (CFStringCompare(window_title, CFSTR("Dock"), 0) == 0) {
+      continue;
+    }
+
     CFNumberRef window_id = reinterpret_cast<CFNumberRef>(
         CFDictionaryGetValue(window, kCGWindowNumber));
     if (!window_id) {
@@ -210,7 +216,10 @@ WindowId GetWindowId(CFDictionaryRef window) {
     return kNullWindowId;
   }
 
-  WindowId id;
+  // Note: WindowId is 64-bit on 64-bit system, but CGWindowID is always 32-bit.
+  // CFNumberGetValue() fills only top 32 bits, so we should use CGWindowID to
+  // receive the window id.
+  CGWindowID id;
   if (!CFNumberGetValue(window_id, kCFNumberIntType, &id)) {
     return kNullWindowId;
   }