Make DisplayInfoProvider an interface

chrome/browser/extensions/api/system_display/display_info_provider.cc

 // Copyright 2013 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/extensions/api/system_display/display_info_provider.h"
 
 #include "base/strings/string_number_conversions.h"
+#include "chrome/common/extensions/api/system_display.h"
 #include "ui/gfx/display.h"
 #include "ui/gfx/screen.h"
 
 namespace extensions {
 
 namespace {
 
+// Created on demand and will leak when the process exits.
+DisplayInfoProvider* g_display_info_provider = NULL;
+
 // Converts Rotation enum to integer.
 int RotationToDegrees(gfx::Display::Rotation rotation) {
   switch (rotation) {
     case gfx::Display::ROTATE_0:
       return 0;
     case gfx::Display::ROTATE_90:
       return 90;
     case gfx::Display::ROTATE_180:
       return 180;
     case gfx::Display::ROTATE_270:
@@ skipping 18 matching lines @@
   unit->bounds.top = bounds.y();
   unit->bounds.width = bounds.width();
   unit->bounds.height = bounds.height();
   unit->work_area.left = work_area.x();
   unit->work_area.top = work_area.y();
   unit->work_area.width = work_area.width();
   unit->work_area.height = work_area.height();
   return unit;
 }
 
-DisplayInfoProvider* g_display_info_provider = NULL;
-
 }  // namespace
 
+DisplayInfoProvider::~DisplayInfoProvider() {
+}
 
-DisplayInfoProvider::DisplayInfoProvider() {}
-
-DisplayInfoProvider::~DisplayInfoProvider() {}
-
+// static
 DisplayInfoProvider* DisplayInfoProvider::Get() {
   if (g_display_info_provider == NULL)
-    g_display_info_provider = new DisplayInfoProvider();
+    g_display_info_provider = DisplayInfoProvider::Create();
   return g_display_info_provider;
 }
 
+// static
 void DisplayInfoProvider::InitializeForTesting(
     DisplayInfoProvider* display_info_provider) {
   DCHECK(display_info_provider);
   g_display_info_provider = display_info_provider;
 }
 
 DisplayInfo DisplayInfoProvider::GetAllDisplaysInfo() {
   // TODO(scottmg): Native is wrong http://crbug.com/133312
   gfx::Screen* screen = gfx::Screen::GetNativeScreen();
   int64 primary_id = screen->GetPrimaryDisplay().id();
   std::vector<gfx::Display> displays = screen->GetAllDisplays();
   DisplayInfo all_displays;
   for (int i = 0; i < screen->GetNumDisplays(); ++i) {
     linked_ptr<extensions::api::system_display::DisplayUnitInfo> unit(
         CreateDisplayUnitInfo(displays[i], primary_id));
     UpdateDisplayUnitInfoForPlatform(displays[i], unit.get());
     all_displays.push_back(unit);
   }
   return all_displays;
 }
 
+DisplayInfoProvider::DisplayInfoProvider() {
+}
+
 }  // namespace extensions