Make memory pressure IPC accessible from content/public.

content/public/browser/memory_pressure.h

Index: content/public/browser/memory_pressure.h
diff --git a/content/public/browser/memory_pressure.h b/content/public/browser/memory_pressure.h
new file mode 100644
index 0000000000000000000000000000000000000000..46a50eca6e51e9d5aa203da9ba69c999e7918d87
--- /dev/null
+++ b/content/public/browser/memory_pressure.h
@@ -0,0 +1,30 @@
+// Copyright (c) 2016 The Chromium Authors. All rights reserved.

[petrcermak, 2016/01/28 09:55:05]

nit: Drop "(c)"
(https://www.chromium.org/developers/coding-style#TOC-File-headers)

[chrisha, 2016/01/28 21:22:14]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CONTENT_PUBLIC_BROWSER_MEMORY_PRESSURE_H_
+#define CONTENT_PUBLIC_BROWSER_MEMORY_PRESSURE_H_
+
+#include "base/memory/memory_pressure_listener.h"
+#include "content/common/content_export.h"
+
+namespace content {
+
+class BrowserChildProcessHost;
+class MemoryMessageFilter;

[Charlie Reis, 2016/01/27 22:34:22]

Why is this needed?

[chrisha, 2016/01/28 21:22:14]

Oops.. cut and paste error. Not needed, and removed.

+class RenderProcessHost;
+
+// Wrappers around singleton member functions in
+// content/browser/memory/memory_pressure_controller. See that header for more

[Charlie Reis, 2016/01/27 22:34:23]

nit: Add .h.

Also, there's no additional details in that header file.  Maybe there should be
more class level comments there?

[chrisha, 2016/01/28 21:22:14]

Added more comments.

+// details. These are exposed so that chrome/browser can interact with the
+// content memory pressure subsystem. These may be called from any thread.
+CONTENT_EXPORT void SendPressureNotification(

[Charlie Reis, 2016/01/27 22:34:22]

I think it's generally preferred to have these in a class rather than global
functions.

From http://www.chromium.org/developers/content-module/content-api:
"content/public should contain only interfaces, structs and (rarely) static
functions"

[chrisha, 2016/01/28 21:22:14]

I only mean to expose a few functions on MemoryPressureController. Should I
wholesale move MemoryPressureController to public/browser/memory, or should I
create a facade that only exposes the few functions external users care about?

+    const BrowserChildProcessHost* child_process_host,
+    base::MemoryPressureListener::MemoryPressureLevel level);
+CONTENT_EXPORT void SendPressureNotification(
+    const RenderProcessHost* render_process_host,
+    base::MemoryPressureListener::MemoryPressureLevel level);
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_MEMORY_MEMORY_PRESSURE_H_