Mac: Fix crash while dragging a tab alone in a window.

chrome/browser/cocoa/tab_view.mm

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "chrome/browser/cocoa/tab_view.h"
 
 #include "base/logging.h"
 #include "chrome/browser/cocoa/nsimage_cache.h"
 #import "chrome/browser/cocoa/tab_controller.h"
 #import "chrome/browser/cocoa/tab_window_controller.h"
@@ skipping 235 matching lines @@
   while (1) {
     theEvent =
     [NSApp nextEventMatchingMask:NSLeftMouseUpMask | NSLeftMouseDraggedMask
                        untilDate:[NSDate distantFuture]
                           inMode:NSDefaultRunLoopMode dequeue:YES];
     NSPoint thisPoint = [NSEvent mouseLocation];
 
     NSEventType type = [theEvent type];
     if (type == NSLeftMouseDragged) {
       [self mouseDragged:theEvent];
-    } else { // Mouse Up
+    } else if (type == NSLeftMouseUp) {
       NSPoint upLocation = [theEvent locationInWindow];
       CGFloat dx = upLocation.x - downLocation.x;
       CGFloat dy = upLocation.y - downLocation.y;
 
       // During rapid tab closure (mashing tab close buttons), we may get hit
       // with a mouse down. As long as the mouse up is over the close button,
       // and the mouse hasn't moved too much, we close the tab.
       if ((dx*dx + dy*dy) <= kRapidCloseDist*kRapidCloseDist &&
           [controller_ inRapidClosureMode]) {
         NSPoint hitLocation =
             [[self superview] convertPoint:[theEvent locationInWindow]
                                   fromView:nil];
         if ([self hitTest:hitLocation] == closeButton_) {
           [controller_ closeTab:self];
           break;
         }
       }
 
       [self mouseUp:theEvent];
       break;
+    } else {
+      // TODO(viettrungluu): [crbug.com/23830] We can receive right-mouse-ups
+      // (and maybe even others?) for reasons I don't understand. So we
+      // explicitly check for both events we're expecting, and log others. We
+      // should figure out what's going on.
+      LOG(WARNING) << "Spurious event received of type " << type << ".";
     }
   }
 }
 
 - (void)mouseDragged:(NSEvent *)theEvent {
   // Special-case this to keep the logic below simpler.
   if (moveWindowOnDrag_) {
     NSPoint thisPoint = [NSEvent mouseLocation];
     NSPoint origin = sourceWindowFrame_.origin;
     origin.x += (thisPoint.x - dragOrigin_.x);
@@ skipping 416 matching lines @@
   [[NSGraphicsContext currentContext] restoreGraphicsState];
 }
 
 // Called when the user hits the right mouse button (or control-clicks) to
 // show a context menu.
 - (void)rightMouseDown:(NSEvent*)theEvent {
   [NSMenu popUpContextMenu:[self menu] withEvent:theEvent forView:self];
 }
 
 @end