Extend Tray click event with position

- Add a parameter to the `click` event of the  `Tray` API object containing the
coordinates of the tray icon/mouse pointer.
The parameter has `x` and `y` fields for the coordinates.
On Mac OS X the coordinates always refer to the position (lower left corner) of
the tray item (NSStatusItem).
On Aura (Linux, Windows) the coordinates refer to the cursor position (which
would be inside the bounding box of the status icon but with slight differences
depending on where effectively the user clicked).

Usage example:

    tray.on('click', function(pos) {
      // pos.x is x coordinate of the tray icon
      // pos.y is y coordinate of the tray icon
      showCustomTrayMenuAt(pos);
    }

FIX nwjs#1874

src/api/tray/tray_aura.cc

@@ -30,6 +30,7 @@
 #include "content/nw/src/api/menu/menu.h"
 #include "content/nw/src/nw_package.h"
 #include "content/nw/src/nw_shell.h"
+#include "ui/gfx/screen.h"
 #include "ui/gfx/image/image.h"
 
 namespace nwapi {
@@ -47,6 +48,12 @@ class TrayObserver : public StatusIconObserver {
 
   virtual void OnStatusIconClicked() OVERRIDE {
     base::ListValue args;
+    base::DictionaryValue* data = new base::DictionaryValue;
+    gfx::Point cursor_pos(
+      gfx::Screen::GetNativeScreen()->GetCursorScreenPoint());
+    data->SetInteger("x", cursor_pos.x());
+    data->SetInteger("y", cursor_pos.y());
+    args.Append(data);
     tray_->dispatcher_host()->SendEvent(tray_, "click", args);
   }
 

src/api/tray/tray_mac.mm

@@ -22,6 +22,7 @@
 
 #include "base/values.h"
 #import <Cocoa/Cocoa.h>
+#include "ui/gfx/screen.h"
 #include "content/nw/src/api/dispatcher_host.h"
 #include "content/nw/src/api/menu/menu.h"
 
@@ -40,6 +41,15 @@ - (void)setBacking:(nwapi::Tray*)newTray {
 }
 - (void)onClick:(id)sender {
     base::ListValue args;
+    base::DictionaryValue* data = new base::DictionaryValue;
+    // Get the position of the frame of the NSStatusItem
+    NSPoint pos = ([[[NSApp currentEvent] window] frame]).origin;
+    // Flip coordinates to gfx (0,0 in top-left corner) using primary screen.
+    NSScreen* screen = [[NSScreen screens] objectAtIndex:0];
+    pos.y = NSMaxY([screen frame]) - pos.y;
+    data->SetInteger("x", pos.x);
+    data->SetInteger("y", pos.y);
+    args.Append(data);
     tray_->dispatcher_host()->SendEvent(tray_,"click",args);
 }
 @end