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

Source/web/WebKit.cpp

Index: Source/web/WebKit.cpp
diff --git a/Source/web/WebKit.cpp b/Source/web/WebKit.cpp
index 6b1bc9394ebc90a076029c3235be48e270bc17f0..f916b41bf2f12e6843812e49a8515dbfeeeb79fc 100644
--- a/Source/web/WebKit.cpp
+++ b/Source/web/WebKit.cpp
@@ -59,6 +59,7 @@
 #include "wtf/Assertions.h"
 #include "wtf/CryptographicallyRandomNumber.h"
 #include "wtf/MainThread.h"
+#include "wtf/Partitions.h"
 #include "wtf/WTF.h"
 #include "wtf/text/AtomicString.h"
 #include "wtf/text/TextEncoding.h"
@@ -289,4 +290,9 @@ void resetPluginCache(bool reloadPages)
     Page::refreshPlugins();
 }
 
+void decommitFreeableMemory()
+{
+    WTF::Partitions::decommitFreeableMemory();
+}
+
 } // namespace blink