Add multi_process_lock to chrome/common

chrome/common/multi_process_lock_win.cc

Index: chrome/common/multi_process_lock_win.cc
diff --git a/chrome/common/multi_process_lock_win.cc b/chrome/common/multi_process_lock_win.cc
new file mode 100644
index 0000000000000000000000000000000000000000..5312f74f38d896ee0c84b0bd24d9882f6237d8d7
--- /dev/null
+++ b/chrome/common/multi_process_lock_win.cc
@@ -0,0 +1,55 @@
+// Copyright (c) 2010 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/common/multi_process_lock.h"
+
+#include "base/logging.h"
+#include "base/utf_string_conversions.h"
+#include "base/win/scoped_handle.h"
+
+class MultiProcessLockWin : public MultiProcessLock {
+ public:
+  explicit MultiProcessLockWin(const std::string& name) : name_(name) { }
+
+  virtual ~MultiProcessLockWin() {
+    if (event_.Get() != NULL) {
+      Unlock();
+    }
+  }
+
+  virtual bool TryLock() {
+    if (event_.Get() != NULL) {
+      DLOG(ERROR) << "MultiProcessLock is already locked - " << name_;
+      return true;
+    }
+    string16 wname = UTF8ToUTF16(name_);
+    HANDLE event = CreateEvent(NULL, FALSE, FALSE, wname.c_str());

[sanjeevr, 2010/11/12 17:47:56]

Nit: You don't need to use a HANDLE here. You could use a ScopedHandle or your
could just the event_ member variable itself and just call reset() if it already
exists. Will make the code more readable.

[dmac, 2010/11/15 23:02:13]

Fixed

+    if (event && GetLastError() != ERROR_ALREADY_EXISTS) {
+      event_.Set(event);
+      return true;
+    } else {
+      if (event) {
+        CloseHandle(event);
+      }
+      return false;
+    }
+  }
+
+  virtual void Unlock() {
+    if (event_.Get() == NULL) {
+      DLOG(ERROR) << "Over unlocked MultiProcessLock - " << name_;
+      return;
+    }
+    event_.Set(NULL);
+  }
+
+ private:
+  std::string name_;
+  base::win::ScopedHandle event_;
+  DISALLOW_COPY_AND_ASSIGN(MultiProcessLockWin);
+};
+
+MultiProcessLock* MultiProcessLock::Create(const std::string &name) {
+  return new MultiProcessLockWin(name);
+}