MemoryPressure: sends the signal to the renderer.

content/browser/renderer_host/render_widget_host_impl.h

Index: content/browser/renderer_host/render_widget_host_impl.h
diff --git a/content/browser/renderer_host/render_widget_host_impl.h b/content/browser/renderer_host/render_widget_host_impl.h
index b79eea67dd779e9641380b20c820218ef6f0c66d..975cded0c08b9bdc1fa912b50d6bd77f3e447b26 100644
--- a/content/browser/renderer_host/render_widget_host_impl.h
+++ b/content/browser/renderer_host/render_widget_host_impl.h
@@ -15,6 +15,7 @@
 
 #include "base/callback.h"
 #include "base/gtest_prod_util.h"
+#include "base/memory/memory_pressure_listener.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
@@ -716,6 +717,9 @@ class CONTENT_EXPORT RenderWidgetHostImpl : virtual public RenderWidgetHost,
   // which may get in recursive loops).
   void DelayedAutoResized();
 
+  // Sends a memory pressure signal to the renderer.
+  void SendMemoryPressureSignal(
+      base::MemoryPressureListener::MemoryPressureLevel level);

[joth, 2013/06/21 21:52:13]

I think you want to do this at the RenderProcess, not RenderWidget level.
otherwise we will send N duplicate messages to each renderer for the N widgets
it hosts.

Also, conceptually do we need this to go to other sandbox child processes? Not
sure if we have common IPC code across process types, but if we do we could
share the message.


Android specific question: couldn't the renderers each listen to
ComponentCallbacks2.onTrimMemory themselves? It is quite possible (and likely)
that a render process will get put into the background kill list before the
browser is.

 
   // Our delegate, which wants to know mainly about keyboard events.
   // It will remain non-NULL until DetachDelegate() is called.
@@ -936,6 +940,8 @@ class CONTENT_EXPORT RenderWidgetHostImpl : virtual public RenderWidgetHost,
 
   BrowserRenderingStats rendering_stats_;
 
+  base::MemoryPressureListener memory_pressure_listener_;
+
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostImpl);
 };