Replace blink::WebDiscardableMemory with base::DiscardableMemory.

third_party/WebKit/Source/platform/PurgeableVector.h

Index: third_party/WebKit/Source/platform/PurgeableVector.h
diff --git a/third_party/WebKit/Source/platform/PurgeableVector.h b/third_party/WebKit/Source/platform/PurgeableVector.h
index 4388749dca31fdd620f5bf1d0c97a8d44c9379f9..6cbaec5e9870b8b4548c12cb64166fc938c14021 100644
--- a/third_party/WebKit/Source/platform/PurgeableVector.h
+++ b/third_party/WebKit/Source/platform/PurgeableVector.h
@@ -31,14 +31,18 @@
 #ifndef PurgeableVector_h
 #define PurgeableVector_h
 
+#include "base/memory/scoped_ptr.h"
 #include "platform/PlatformExport.h"
 #include "wtf/Forward.h"
 #include "wtf/Noncopyable.h"
 #include "wtf/Vector.h"
 
+namespace base {
+class DiscardableMemory;
+}
+
 namespace blink {
 
-class WebDiscardableMemory;
 class WebProcessMemoryDump;
 
 // A simple vector implementation that supports purgeable memory. The vector is
@@ -115,7 +119,7 @@ private:
     // Note that there can't be data both in |m_vector| and
     // |m_discardable|, i.e. only one of them is used at a given time.
     Vector<char> m_vector;
-    OwnPtr<WebDiscardableMemory> m_discardable;
+    scoped_ptr<base::DiscardableMemory> m_discardable;
     size_t m_discardableCapacity;
     size_t m_discardableSize;
     bool m_isPurgeable;