Cleanup: Pull some browser keep alive functions into its own file.

chrome/browser/ui/window_sizer/window_sizer_ash_uitest.cc

Index: chrome/browser/ui/window_sizer/window_sizer_ash_uitest.cc
diff --git a/chrome/browser/ui/window_sizer/window_sizer_ash_uitest.cc b/chrome/browser/ui/window_sizer/window_sizer_ash_uitest.cc
index 51a71ab4a8e60cafae128e46a2d607dff731acbb..7e7d70dbbd0b62f4ce6f3e058ad31c7bdcd49280 100644
--- a/chrome/browser/ui/window_sizer/window_sizer_ash_uitest.cc
+++ b/chrome/browser/ui/window_sizer/window_sizer_ash_uitest.cc
@@ -10,6 +10,7 @@
 #include "base/location.h"
 #include "base/message_loop/message_loop.h"
 #include "chrome/browser/lifetime/application_lifetime.h"
+#include "chrome/browser/lifetime/browser_keep_alive.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_list.h"
 #include "chrome/browser/ui/browser_window.h"
@@ -79,7 +80,7 @@ void OpenBrowserUsingShelfOnRootWindow(aura::Window* root_window) {
 IN_PROC_BROWSER_TEST_F(WindowSizerTest,
                        MAYBE_OpenBrowserUsingShelfOnOtherDisplay) {
   // Don't shutdown when closing the last browser window.
-  chrome::IncrementKeepAliveCount();
+  browser_lifetime::ScopedKeepAlive scoped_keep_alive;
 
   aura::Window::Windows root_windows = ash::Shell::GetAllRootWindows();
 
@@ -111,9 +112,6 @@ IN_PROC_BROWSER_TEST_F(WindowSizerTest,
   EXPECT_EQ(root_windows[0],
             browser_list->get(0)->window()->GetNativeWindow()->GetRootWindow());
   EXPECT_EQ(root_windows[0], ash::Shell::GetTargetRootWindow());
-
-  // Balanced with the chrome::IncrementKeepAliveCount above.
-  chrome::DecrementKeepAliveCount();
 }
 
 namespace {
@@ -166,7 +164,7 @@ void OpenBrowserUsingContextMenuOnRootWindow(aura::Window* root_window) {
 IN_PROC_BROWSER_TEST_F(WindowSizerContextMenuTest,
                        MAYBE_OpenBrowserUsingContextMenuOnOtherDisplay) {
   // Don't shutdown when closing the last browser window.
-  chrome::IncrementKeepAliveCount();
+  browser_lifetime::ScopedKeepAlive scoped_keep_alive;
 
   views::MenuController::TurnOffMenuSelectionHoldForTest();
 
@@ -194,7 +192,4 @@ IN_PROC_BROWSER_TEST_F(WindowSizerContextMenuTest,
   EXPECT_EQ(root_windows[0],
             browser_list->get(1)->window()->GetNativeWindow()->GetRootWindow());
   EXPECT_EQ(root_windows[0], ash::Shell::GetTargetRootWindow());
-
-  // Balanced with the chrome::IncrementKeepAliveCount above.
-  chrome::DecrementKeepAliveCount();
 }