Added Google Cache Invalidation library to DEPS and got it to compile

third_party/cacheinvalidation/overrides/google/cacheinvalidation/mutex.h

Index: third_party/cacheinvalidation/overrides/google/cacheinvalidation/mutex.h
diff --git a/third_party/cacheinvalidation/overrides/google/cacheinvalidation/mutex.h b/third_party/cacheinvalidation/overrides/google/cacheinvalidation/mutex.h
new file mode 100644
index 0000000000000000000000000000000000000000..b99dcee0b3d634bf376178e8d52a2427cca8e2bf
--- /dev/null
+++ b/third_party/cacheinvalidation/overrides/google/cacheinvalidation/mutex.h
@@ -0,0 +1,26 @@
+// 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.
+
+#ifndef GOOGLE_CACHEINVALIDATION_MUTEX_H_
+#define GOOGLE_CACHEINVALIDATION_MUTEX_H_
+
+#include "base/lock.h"
+#include "base/logging.h"
+
+namespace invalidation {
+
+typedef ::Lock Mutex;
+
+class MutexLock {
+ public:
+  explicit MutexLock(Mutex* m) : auto_lock_(*m) {}
+
+ private:
+  AutoLock auto_lock_;
+  DISALLOW_COPY_AND_ASSIGN(MutexLock);
+};
+
+}  // namespace invalidation
+
+#endif  // GOOGLE_CACHEINVALIDATION_MUTEX_H_