Disable system suspend while downloading files on win32.

If the system goes into power-save sleep mode while downloading files,
the download fails. So, prevent sleep mode until the download finishes.

This patch introduces a new RAII class to request that the system's
power-save mode be disabled - PowerSaveBlocker.
This is only implemented for win32; other platforms are stubbed out.

This only partially implements bug 25420 it only attempts to handle the
downloading case.

Patch by Bryan Donlan <bdonlan@gmail.com>

BUG=25420
TEST=Download a large file with the system sleep timeout set to a short interval.
Review URL: http://codereview.chromium.org/287017

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@29873 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 42 insertions, 0 deletions

diff --git a/chrome/browser/power_save_blocker.h b/chrome/browser/power_save_blocker.h
new file mode 100644
index 0000000..f362915
--- /dev/null
+++ b/chrome/browser/power_save_blocker.h
@@ -0,0 +1,42 @@
+// Copyright (c) 2009 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.
+
+#ifndef CHROME_BROWSER_POWER_SAVE_BLOCKER_H_
+#define CHROME_BROWSER_POWER_SAVE_BLOCKER_H_
+
+#include "base/basictypes.h"
+
+// A RAII-style class to block the system from entering low-power
+// (sleep) mode.
+class PowerSaveBlocker {
+ public:
+  explicit PowerSaveBlocker(bool enabled);
+  ~PowerSaveBlocker();
+
+  bool enabled() const { return enabled_; }
+
+  // Puts the sleep mode block into effect.
+  void Enable();
+  // Disables the sleep block.
+  void Disable();
+
+ private:
+  // Platform-specific function called when enable state is changed.
+  // Guarenteed to be called only from the UI thread.
+  static void ApplyBlock(bool blocked);
+
+  // Called only from UI thread.
+  static void AdjustBlockCount(int delta);
+
+  // Invokes AdjustBlockCount on the UI thread.
+  static void PostAdjustBlockCount(int delta);
+
+  bool enabled_;
+
+  static int blocker_count_;
+
+  DISALLOW_COPY_AND_ASSIGN(PowerSaveBlocker);
+};
+
+#endif  // CHROME_BROWSER_POWER_SAVE_BLOCKER_H_