Expose ReleaseFreeMemory to free up memory on memory pressure or idle cleanup.

public/web/WebKit.h

Index: public/web/WebKit.h
diff --git a/public/web/WebKit.h b/public/web/WebKit.h
index 24e267caddf4d633d3c099a18a62300d531549a3..822a3b8452ee1fb726307debbf726dec3dee8af8 100644
--- a/public/web/WebKit.h
+++ b/public/web/WebKit.h
@@ -85,6 +85,9 @@ BLINK_EXPORT void enableLogChannel(const char*);
 // containing plugins will be reloaded after refreshing the plugin list.
 BLINK_EXPORT void resetPluginCache(bool reloadPages = false);
 
+// Decommit freeable memory pages.

[Rick Byers, 2015/06/05 17:35:46]

nit: This is just for tooling scenarios, right?  It would be nice if the comment
indicated when/how this should be used - eg. "Intended to be used only by memory
monitoring performance tools".  Like forcing a GC I'd expect you normally
wouldn't want callers invoking this in non-tooling scenarios, right?

[Primiano Tucci (use gerrit), 2015/06/05 18:24:50]

Nope, this is going to be an actual memory saving thing (yay).
As the title suggests we are going to call this during long idle pauses and on
memory pressure.
We figured out while writing the tools (it's going to save 200-800k per renderer
process) :)
See the case study this doc for details:
https://docs.google.com/document/d/1zBuz0WVBTReoj0gXooihTFPwMQQkCkQGy0Cl9lSwU...

+BLINK_EXPORT void decommitFreeableMemory();
+
 } // namespace blink
 
 #endif