Replace blink::WebDiscardableMemory with base::DiscardableMemory.

third_party/WebKit/public/platform/WebDiscardableMemory.h

-/*
- * Copyright (C) 2013 Google Inc. All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * 1.  Redistributions of source code must retain the above copyright
- *     notice, this list of conditions and the following disclaimer.
- * 2.  Redistributions in binary form must reproduce the above copyright
- *     notice, this list of conditions and the following disclaimer in the
- *     documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
- * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
- * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
- * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
- * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
- * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
- * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
- * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
- * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-#ifndef WebDiscardableMemory_h
-#define WebDiscardableMemory_h
-
-namespace blink {
-
-class WebMemoryAllocatorDump;
-class WebProcessMemoryDump;
-class WebString;
-
-// A memory allocation that can be automatically discarded by the operating
-// system under memory pressure.
-//
-// Discardable usage is typically:
-//    WebDiscardableMemory* mem = allocateAndLockedDiscardableMemory(1024*1024);
-//    void* data = mem->data();
-//    memset(data, 3, 1024*1024);
-//    mem->unlock();
-//
-// Later, when you need it again:
-//    if (!mem->lock()) {
-//       ... handle the fact that the memory is gone...
-//       delete mem; // Make sure to destroy it. It is never going to come back.
-//       return;
-//    }
-//    ... use mem->data() as much as you want
-//    mem->unlock();
-//
-class WebDiscardableMemory {
-public:
-    // Must not be called while locked.
-    virtual ~WebDiscardableMemory() { }
-
-    // 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.
-    //
-    // Nested calls to lock are not allowed.
-    virtual bool lock() = 0;
-
-    // Returns the current pointer for the discardable memory. This call is ONLY
-    // valid when the discardable memory object is locked.
-    virtual void* data() = 0;
-
-    // Unlock the memory so that it can be purged by the system. Must be called
-    // after every successful lock call.
-    virtual void unlock() = 0;
-
-    // Used for tracing the statistics of discardable memory allocated. Returns
-    // a new MemoryAllocatorDump in the WebProcessMemoryDump object provided,
-    // with the size of the discardable memory. The MemoryAllocatorDump created
-    // is owned by the WebProcessMemoryDump object.
-    // See WebProcessMemoryDump::createMemoryAllocatorDump.
-    virtual WebMemoryAllocatorDump* createMemoryAllocatorDump(const WebString& name, WebProcessMemoryDump*) const = 0;
-};
-
-} // namespace blink
-
-#endif