MacViews: Fix failing mouse capture unittests.

ui/views/cocoa/cocoa_mouse_capture.mm

Index: ui/views/cocoa/cocoa_mouse_capture.mm
diff --git a/ui/views/cocoa/cocoa_mouse_capture.mm b/ui/views/cocoa/cocoa_mouse_capture.mm
index 17d34ec5bfd30fc549d42f8e2fee77fc7d25702b..74c6a7c69eafc3fda494a9bbb12e7292c9e46d43 100644
--- a/ui/views/cocoa/cocoa_mouse_capture.mm
+++ b/ui/views/cocoa/cocoa_mouse_capture.mm
@@ -20,9 +20,17 @@ class CocoaMouseCapture::ActiveEventTap {
  public:
   explicit ActiveEventTap(CocoaMouseCapture* owner);
   ~ActiveEventTap();
+
+  // Returns the NSWindow with capture or nil if no window has capture
+  // currently.
+  static NSWindow* GetGlobalCaptureWindow();
+
   void Init();
 
  private:
+  // Returns the associated NSWindow with capture.
+  NSWindow* GetCaptureWindow() const;
+
   // The currently active event tap, or null if there is none.
   static ActiveEventTap* g_active_event_tap;
 
@@ -52,6 +60,11 @@ CocoaMouseCapture::ActiveEventTap::~ActiveEventTap() {
   owner_->delegate_->OnMouseCaptureLost();
 }
 
+// static
+NSWindow* CocoaMouseCapture::ActiveEventTap::GetGlobalCaptureWindow() {
+  return g_active_event_tap ? g_active_event_tap->GetCaptureWindow() : nil;
+}
+
 void CocoaMouseCapture::ActiveEventTap::Init() {
   NSEventMask event_mask =
       NSLeftMouseDownMask | NSLeftMouseUpMask | NSRightMouseDownMask |
@@ -71,6 +84,10 @@ void CocoaMouseCapture::ActiveEventTap::Init() {
       }];
 }
 
+NSWindow* CocoaMouseCapture::ActiveEventTap::GetCaptureWindow() const {
+  return owner_->delegate_->GetWindow();
+}
+
 CocoaMouseCapture::CocoaMouseCapture(CocoaMouseCaptureDelegate* delegate)
     : delegate_(delegate), active_handle_(new ActiveEventTap(this)) {
   active_handle_->Init();
@@ -79,6 +96,11 @@ CocoaMouseCapture::CocoaMouseCapture(CocoaMouseCaptureDelegate* delegate)
 CocoaMouseCapture::~CocoaMouseCapture() {
 }
 
+// static
+NSWindow* CocoaMouseCapture::GetGlobalCaptureWindow() {
+  return ActiveEventTap::GetGlobalCaptureWindow();
+}
+
 void CocoaMouseCapture::OnOtherClientGotCapture() {
   DCHECK(active_handle_);
   active_handle_.reset();