Add missing (and remove superfluous) 'explicit' from constructors.

chrome/browser/ui/cocoa/panels/panel_cocoa_unittest.mm

 // Copyright (c) 2012 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.
 
 #include <Carbon/Carbon.h>
 #import <Cocoa/Cocoa.h>
 
 #include "base/command_line.h"
 #include "base/debug/debugger.h"
 #include "base/mac/scoped_nsautorelease_pool.h"
@@ skipping 10 matching lines @@
 #include "chrome/browser/ui/panels/panel_manager.h"
 #include "chrome/common/chrome_notification_types.h"
 #include "chrome/common/chrome_switches.h"
 #include "content/public/test/test_utils.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/gtest_mac.h"
 
 class PanelAnimatedBoundsObserver :
     public content::WindowedNotificationObserver {
  public:
-  PanelAnimatedBoundsObserver(Panel* panel)
+  explicit PanelAnimatedBoundsObserver(Panel* panel)
     : content::WindowedNotificationObserver(
         chrome::NOTIFICATION_PANEL_BOUNDS_ANIMATIONS_FINISHED,
         content::Source<Panel>(panel)) { }
   virtual ~PanelAnimatedBoundsObserver() { }
 };
 
 // Main test class.
 class PanelCocoaTest : public CocoaProfileTest {
  public:
   virtual void SetUp() {
@@ skipping 369 matching lines @@
   NSWindow* frontmostWindow = [[NSApp orderedWindows] objectAtIndex:0];
   EXPECT_NSEQ(frontmostWindow, [native_window->controller_ window]);
 
   native_window2->ActivatePanel();
   frontmostWindow = [[NSApp orderedWindows] objectAtIndex:0];
   EXPECT_NSEQ(frontmostWindow, [native_window2->controller_ window]);
 
   ClosePanelAndWait(panel);
   ClosePanelAndWait(panel2);
 }