Allow a Frame Background Context Menu on Mac

This brings the frame context menu available on other platforms to Mac
and allows users to restore the previously closed tab within the
tabstrip.

BUG=997637
TEST=Right clicking at frame and contents boundaries in tabbed Chrome.

Change-Id: I3c4129641d398e38786cfa7d501edc32f2e92252
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1786935
Auto-Submit: Robert Liao <robliao@chromium.org>
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Robert Liao <robliao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#694319}

chrome/browser/ui/views/frame/browser_frame_mac.mm

@@ -372,7 +372,7 @@ bool BrowserFrameMac::UseCustomFrame() const {
 }
 
 bool BrowserFrameMac::UsesNativeSystemMenu() const {
-  return true;
+  return false;
 }
 
 bool BrowserFrameMac::ShouldSaveWindowPlacement() const {

components/remote_cocoa/app_shim/native_widget_mac_nswindow.mm

@@ -230,17 +230,34 @@
     return;
 
   NSEventType type = [event type];
-  if ((type != NSKeyDown && type != NSKeyUp) || ![self hasViewsMenuActive]) {
-    [super sendEvent:event];
-    return;
+
+  // Draggable regions only respond to left-click dragging, but the system will
+  // still suppress right-clicks in a draggable region. Forwarding right-clicks
+  // allows the underlying views to respond to right-click to potentially bring
+  // up a frame context menu.
+  if (type == NSRightMouseDown) {
+    if ([[self contentView] hitTest:event.locationInWindow] == nil) {
+      [[self contentView] rightMouseDown:event];
+      return;
+    }
+  } else if (type == NSRightMouseUp) {
+    if ([[self contentView] hitTest:event.locationInWindow] == nil) {
+      [[self contentView] rightMouseUp:event];
+      return;
+    }
+  } else if ([self hasViewsMenuActive]) {
+    // Send to the menu, after converting the event into an action message using
+    // the content view.
+    if (type == NSKeyDown) {
+      [[self contentView] keyDown:event];
+      return;
+    } else if (type == NSKeyUp) {
+      [[self contentView] keyUp:event];
+      return;
+    }
   }
 
-  // Send to the menu, after converting the event into an action message using
-  // the content view.
-  if (type == NSKeyDown)
-    [[self contentView] keyDown:event];
-  else
-    [[self contentView] keyUp:event];
+  [super sendEvent:event];
 }
 
 // Override window order functions to intercept other visibility changes. This