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, 58 insertions, 0 deletions

diff --git a/chrome/browser/power_save_blocker_common.cc b/chrome/browser/power_save_blocker_common.cc
new file mode 100644
index 0000000..b6ff2ac
--- /dev/null
+++ b/chrome/browser/power_save_blocker_common.cc
@@ -0,0 +1,58 @@
+// 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.
+
+#include "chrome/browser/power_save_blocker.h"
+#include "chrome/browser/chrome_thread.h"
+
+// Accessed only from the UI thread.
+int PowerSaveBlocker::blocker_count_ = 0;
+
+PowerSaveBlocker::PowerSaveBlocker(bool enable) : enabled_(false) {
+  if (enable)
+    Enable();
+}
+
+PowerSaveBlocker::~PowerSaveBlocker(void) {
+  Disable();
+}
+
+void PowerSaveBlocker::Enable() {
+  if (enabled_)
+    return;
+
+  enabled_ = true;
+  PostAdjustBlockCount(1);
+}
+
+void PowerSaveBlocker::Disable() {
+  if (!enabled_)
+    return;
+
+  enabled_ = false;
+  PostAdjustBlockCount(-1);
+}
+
+
+void PowerSaveBlocker::PostAdjustBlockCount(int delta) {
+  MessageLoop *ml = ChromeThread::GetMessageLoop(ChromeThread::UI);
+
+  ml->PostTask(FROM_HERE,
+      NewRunnableFunction(&PowerSaveBlocker::AdjustBlockCount, delta));
+}
+
+// Called only from UI thread.
+void PowerSaveBlocker::AdjustBlockCount(int delta) {
+  DCHECK(ChromeThread::CurrentlyOn(ChromeThread::UI));
+
+  bool was_blocking = (blocker_count_ != 0);
+
+  blocker_count_ += delta;
+
+  bool is_blocking = (blocker_count_ != 0);
+
+  DCHECK_GE(blocker_count_, 0);
+
+  if (is_blocking != was_blocking)
+    ApplyBlock(is_blocking);
+}