Added MemoryMonitor for Linux (with test)

components/memory_coordinator/browser/test_memory_monitor.h

Index: components/memory_coordinator/browser/test_memory_monitor.h
diff --git a/components/memory_coordinator/browser/test_memory_monitor.h b/components/memory_coordinator/browser/test_memory_monitor.h
new file mode 100644
index 0000000000000000000000000000000000000000..a9e1f8148ea3578b2f57035f7ddb855b0a8fc82e
--- /dev/null
+++ b/components/memory_coordinator/browser/test_memory_monitor.h
@@ -0,0 +1,38 @@
+// Copyright (c) 2016 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 "components/memory_coordinator/browser/memory_monitor.h"
+
+#include "base/process/process_metrics.h"
+
+namespace memory_coordinator {
+
+// A delegate that allows mocking the various inputs to MemoryMonitor.
+class TestMemoryMonitorDelegate : public MemoryMonitorDelegate {
+ public:
+  TestMemoryMonitorDelegate() : calls_(0) { mem_info_ = {}; }
+  ~TestMemoryMonitorDelegate() override;
+
+  void GetSystemMemoryInfo(base::SystemMemoryInfoKB* mem_info) override;
+
+  size_t calls() const { return calls_; }
+  void ResetCalls() { calls_ = 0; }
+
+  void SetTotalMemoryKB(int total_memory_kb) {
+    mem_info_.total = total_memory_kb;
+  }
+
+ protected:
+  // Because the fields of SystemMemoryInfoKB vary depending on the operating
+  // system, specific derived classes will have to provide methods to load
+  // values into |mem_info_|;
+  base::SystemMemoryInfoKB mem_info_;
+
+ private:
+  size_t calls_;
+
+  DISALLOW_COPY_AND_ASSIGN(TestMemoryMonitorDelegate);
+};
+
+}  // namespace memory_coordinator