DISALLOW_COPY_AND_ASSIGN the TabStripModelObserver.

Disable the implicitly generated special functions that perform copies and moves
according to the Google C++ Style Guide.

BUG=None

Review-Url: https://codereview.chromium.org/2595313002
Cr-Commit-Position: refs/heads/master@{#442871}

chrome/browser/ui/tabs/tab_strip_model_observer.cc

@@ -6,6 +6,9 @@
 
 using content::WebContents;
 
+TabStripModelObserver::TabStripModelObserver() {
+}
+
 void TabStripModelObserver::TabInsertedAt(TabStripModel* tab_strip_model,
                                           WebContents* contents,
                                           int index,

chrome/browser/ui/tabs/tab_strip_model_observer.h

@@ -5,6 +5,8 @@
 #ifndef CHROME_BROWSER_UI_TABS_TAB_STRIP_MODEL_OBSERVER_H_
 #define CHROME_BROWSER_UI_TABS_TAB_STRIP_MODEL_OBSERVER_H_
 
+#include "base/macros.h"
+
 class TabStripModel;
 
 namespace content {
@@ -152,7 +154,11 @@ class TabStripModelObserver {
   virtual void CloseAllTabsCanceled();
 
  protected:
+  TabStripModelObserver();
   virtual ~TabStripModelObserver() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(TabStripModelObserver);
 };
 
 #endif  // CHROME_BROWSER_UI_TABS_TAB_STRIP_MODEL_OBSERVER_H_