Add option to disallow the discarding of a tab that was previously discarded.

chrome/browser/ui/tabs/tab_discard_state.cc

+// Copyright 2015 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 "chrome/browser/ui/tabs/tab_discard_state.h"
+
+#include "content/public/browser/web_contents.h"
+
+using content::WebContents;
+
+namespace {
+
+const char kDiscardStateKey[] = "TabDiscardState";
+
+}  // namespace
+
+// static
+TabDiscardState* TabDiscardState::Get(WebContents* web_contents) {
+  TabDiscardState* discard_state = static_cast<TabDiscardState*>(
+      web_contents->GetUserData(&kDiscardStateKey));
+
+  // If this function is called, we probably need to query/change the discard
+  // state. Let's go ahead a add one.
+  if (!discard_state) {
+    discard_state = new TabDiscardState;
+    web_contents->SetUserData(&kDiscardStateKey, discard_state);
+  }
+
+  return discard_state;
+}
+
+// static
+void TabDiscardState::Set(WebContents* web_contents, TabDiscardState* state) {
+  web_contents->SetUserData(&kDiscardStateKey, state);
+}
+
+// static
+bool TabDiscardState::IsDiscarded(WebContents* web_contents) {
+  TabDiscardState* discard_state = TabDiscardState::Get(web_contents);
+  return discard_state->is_discarded_;
+}
+
+// static
+void TabDiscardState::SetDiscardState(WebContents* web_contents, bool state) {
+  TabDiscardState* discard_state = TabDiscardState::Get(web_contents);
+  discard_state->is_discarded_ = state;
+}
+
+// static
+int TabDiscardState::DiscardCount(WebContents* web_contents) {
+  TabDiscardState* discard_state = TabDiscardState::Get(web_contents);
+  return discard_state->discard_count_;
+}
+
+// static
+void TabDiscardState::IncrementDiscardCount(WebContents* web_contents) {
+  TabDiscardState* discard_state = TabDiscardState::Get(web_contents);
+  discard_state->discard_count_++;
+}
+
+// static
+void TabDiscardState::CopyState(content::WebContents* old_contents,
+                                content::WebContents* new_contents) {
+  TabDiscardState* old_state = Get(old_contents);
+  TabDiscardState* new_State = Get(new_contents);
+  *new_State = *old_state;
+}