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diff --git a/third_party/base/allocator/partition_allocator/page_allocator.h b/third_party/base/allocator/partition_allocator/page_allocator.h
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+++ b/third_party/base/allocator/partition_allocator/page_allocator.h
@@ -0,0 +1,126 @@
+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_H
+#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_H
+
+#include <stdint.h>
+
+#include <cstddef>
+
+#include "third_party/base/base_export.h"
+#include "third_party/base/compiler_specific.h"
+#include "third_party/build/build_config.h"
+
+namespace pdfium {
+namespace base {
+
+#if defined(OS_WIN)
+static const size_t kPageAllocationGranularityShift = 16;  // 64KB
+#else
+static const size_t kPageAllocationGranularityShift = 12;  // 4KB
+#endif
+static const size_t kPageAllocationGranularity =
+    1 << kPageAllocationGranularityShift;
+static const size_t kPageAllocationGranularityOffsetMask =
+    kPageAllocationGranularity - 1;
+static const size_t kPageAllocationGranularityBaseMask =
+    ~kPageAllocationGranularityOffsetMask;
+
+// All Blink-supported systems have 4096 sized system pages and can handle
+// permissions and commit / decommit at this granularity.
+static const size_t kSystemPageSize = 4096;
+static const size_t kSystemPageOffsetMask = kSystemPageSize - 1;
+static const size_t kSystemPageBaseMask = ~kSystemPageOffsetMask;
+
+enum PageAccessibilityConfiguration {
+  PageAccessible,
+  PageInaccessible,
+};
+
+// Allocate one or more pages.
+// The requested address is just a hint; the actual address returned may
+// differ. The returned address will be aligned at least to align bytes.
+// len is in bytes, and must be a multiple of kPageAllocationGranularity.
+// align is in bytes, and must be a power-of-two multiple of
+// kPageAllocationGranularity.
+// If addr is null, then a suitable and randomized address will be chosen
+// automatically.
+// PageAccessibilityConfiguration controls the permission of the
+// allocated pages.
+// This call will return null if the allocation cannot be satisfied.
+BASE_EXPORT void* AllocPages(void* address,
+                             size_t len,
+                             size_t align,
+                             PageAccessibilityConfiguration);
+
+// Free one or more pages.
+// addr and len must match a previous call to allocPages().
+BASE_EXPORT void FreePages(void* address, size_t length);
+
+// Mark one or more system pages as being inaccessible.
+// Subsequently accessing any address in the range will fault, and the
+// addresses will not be re-used by future allocations.
+// len must be a multiple of kSystemPageSize bytes.
+BASE_EXPORT void SetSystemPagesInaccessible(void* address, size_t length);
+
+// Mark one or more system pages as being accessible.
+// The pages will be readable and writeable.
+// len must be a multiple of kSystemPageSize bytes.
+// The result bool value indicates whether the permission
+// change succeeded or not. You must check the result
+// (in most cases you need to CHECK that it is true).
+BASE_EXPORT WARN_UNUSED_RESULT bool SetSystemPagesAccessible(void* address,
+                                                             size_t length);
+
+// Decommit one or more system pages. Decommitted means that the physical memory
+// is released to the system, but the virtual address space remains reserved.
+// System pages are re-committed by calling recommitSystemPages(). Touching
+// a decommitted page _may_ fault.
+// Clients should not make any assumptions about the contents of decommitted
+// system pages, before or after they write to the page. The only guarantee
+// provided is that the contents of the system page will be deterministic again
+// after recommitting and writing to it. In particlar note that system pages are
+// not guaranteed to be zero-filled upon re-commit. len must be a multiple of
+// kSystemPageSize bytes.
+BASE_EXPORT void DecommitSystemPages(void* address, size_t length);
+
+// Recommit one or more system pages. Decommitted system pages must be
+// recommitted before they are read are written again.
+// Note that this operation may be a no-op on some platforms.
+// len must be a multiple of kSystemPageSize bytes.
+BASE_EXPORT void RecommitSystemPages(void* address, size_t length);
+
+// Discard one or more system pages. Discarding is a hint to the system that
+// the page is no longer required. The hint may:
+// - Do nothing.
+// - Discard the page immediately, freeing up physical pages.
+// - Discard the page at some time in the future in response to memory pressure.
+// Only committed pages should be discarded. Discarding a page does not
+// decommit it, and it is valid to discard an already-discarded page.
+// A read or write to a discarded page will not fault.
+// Reading from a discarded page may return the original page content, or a
+// page full of zeroes.
+// Writing to a discarded page is the only guaranteed way to tell the system
+// that the page is required again. Once written to, the content of the page is
+// guaranteed stable once more. After being written to, the page content may be
+// based on the original page content, or a page of zeroes.
+// len must be a multiple of kSystemPageSize bytes.
+BASE_EXPORT void DiscardSystemPages(void* address, size_t length);
+
+ALWAYS_INLINE uintptr_t RoundUpToSystemPage(uintptr_t address) {
+  return (address + kSystemPageOffsetMask) & kSystemPageBaseMask;
+}
+
+ALWAYS_INLINE uintptr_t RoundDownToSystemPage(uintptr_t address) {
+  return address & kSystemPageBaseMask;
+}
+
+// Returns errno (or GetLastError code) when mmap (or VirtualAlloc) fails.
+BASE_EXPORT uint32_t GetAllocPageErrorCode();
+
+}  // namespace base
+}  // namespace pdfium
+
+#endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PAGE_ALLOCATOR_H