Add WTF::DiscardableMemory.

Source/wtf/DiscardableMemory.h

Index: Source/wtf/DiscardableMemory.h
diff --git a/public/platform/WebDiscardableMemory.h b/Source/wtf/DiscardableMemory.h
similarity index 87%
copy from public/platform/WebDiscardableMemory.h
copy to Source/wtf/DiscardableMemory.h
index 0cdcfe383859b18f11da4db7a170b3fe5ea29879..217034d7ab97ac41dbe0a952ec6baa329fa76444 100644
--- a/public/platform/WebDiscardableMemory.h
+++ b/Source/wtf/DiscardableMemory.h
@@ -23,16 +23,16 @@
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef WebDiscardableMemory_h
-#define WebDiscardableMemory_h
+#ifndef WTF_DiscardableMemory_h
+#define WTF_DiscardableMemory_h
 
-namespace blink {
+namespace WTF {
 
 // A memory allocation that can be automatically discarded by the operating
 // system under memory pressure.
 //
 // Discardable usage is typically:
-//    WebDiscardableMemory* mem = allocateAndLockedDiscardableMemory(1024*1024);
+//    DiscardableMemory* mem = WTFPlatform::getInstance()->allocateAndLockedDiscardableMemory(1024*1024);
 //    void* data = mem->data();
 //    memset(data, 3, 1024*1024);
 //    mem->unlock();
@@ -46,17 +46,17 @@ namespace blink {
 //    ... use mem->data() as much as you want
 //    mem->unlock();
 //
-class WebDiscardableMemory {
+class DiscardableMemory {
 public:
     // Must not be called while locked.
-    virtual ~WebDiscardableMemory() { }
+    virtual ~DiscardableMemory() { }
 
     // Locks the memory, prevent it from being discarded. Once locked. you may
     // obtain a pointer to that memory using the data() method.
     //
     // lock() may return false, indicating that the underlying memory was
-    // discarded and that the lock failed. In this case, the
-    // WebDiscardableMemory is effectively dead.
+    // discarded and that the lock failed. In this case, the DiscardableMemory
+    // is effectively dead.
     //
     // Nested calls to lock are not allowed.
     virtual bool lock() = 0;
@@ -70,6 +70,6 @@ public:
     virtual void unlock() = 0;
 };
 
-} // namespace blink
+} // namespace WTF
 
 #endif