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..0dcd5cf3699560949de1462eada9b0d6917470df 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 +290,12 @@ void resetPluginCache(bool reloadPages)
     Page::refreshPlugins();
 }
 
+void ReleaseFreeMemory()

[Primiano Tucci (use gerrit), 2015/06/02 17:18:55]

nit: lowercase r (releaseFreeMemory)

+{
+    WTF::partitionPurgeMemory(WTF::Partitions::getBufferPartition());

[Primiano Tucci (use gerrit), 2015/06/02 17:18:55]

Hmm threading..
I think that here you need:
1) ASSERT(isMainThread()) for the object model and rendering partitions
2) Take the lock for the other two partitions.

Also, I would move these four lines to Partitions.cpp, expose this method there,
and here just call the method in Partitions.h.

Rationale: the knowledge about the existing partitions should be all in one
place, not spread out.

+    WTF::partitionPurgeMemory(WTF::Partitions::getFastMallocPartition());
+    WTF::partitionPurgeMemory(WTF::Partitions::getObjectModelPartition());
+    WTF::partitionPurgeMemory(WTF::Partitions::getRenderingPartition());
+}
+
 } // namespace blink