[win32] Improve random mmap address generation on 64-bit.

src/base/platform/platform-win32.cc

Index: src/base/platform/platform-win32.cc
diff --git a/src/base/platform/platform-win32.cc b/src/base/platform/platform-win32.cc
index 07c0bc3ebf76423d2df3312fcfdd5617e3476f9e..4328039c22859a25beb7c3782834014ca1354cf8 100644
--- a/src/base/platform/platform-win32.cc
+++ b/src/base/platform/platform-win32.cc
@@ -733,15 +733,17 @@ void* OS::GetRandomMmapAddr() {
   // Note: This does not guarantee RWX regions will be within the
   // range kAllocationRandomAddressMin to kAllocationRandomAddressMax
 #ifdef V8_HOST_ARCH_64_BIT
-  static const intptr_t kAllocationRandomAddressMin = 0x0000000080000000;
-  static const intptr_t kAllocationRandomAddressMax = 0x000003FFFFFF0000;
+  static const uintptr_t kAllocationRandomAddressMin = 0x0000000080000000;
+  static const uintptr_t kAllocationRandomAddressMax = 0x000003FFFFFF0000;
 #else
-  static const intptr_t kAllocationRandomAddressMin = 0x04000000;
-  static const intptr_t kAllocationRandomAddressMax = 0x3FFF0000;
+  static const uintptr_t kAllocationRandomAddressMin = 0x04000000;
+  static const uintptr_t kAllocationRandomAddressMax = 0x3FFF0000;
 #endif
-  uintptr_t address =
-      (platform_random_number_generator.Pointer()->NextInt() << kPageSizeBits) |
-      kAllocationRandomAddressMin;
+  uintptr_t address;
+  platform_random_number_generator.Pointer()->NextBytes(&address,
+                                                        sizeof(address));
+  address <<= kPageSizeBits;
+  address += kAllocationRandomAddressMin;
   address &= kAllocationRandomAddressMax;
   return reinterpret_cast<void *>(address);
 }