Fix PartitionAlloc randomization on 32-bit systems

third_party/WebKit/Source/wtf/AddressSpaceRandomization.cpp

Index: third_party/WebKit/Source/wtf/AddressSpaceRandomization.cpp
diff --git a/third_party/WebKit/Source/wtf/AddressSpaceRandomization.cpp b/third_party/WebKit/Source/wtf/AddressSpaceRandomization.cpp
index 2a363a33e306649fdf2dfc68a43e537f20a8d937..7f98d9dcac7e5b586ff7696a68230652a8a5f25d 100644
--- a/third_party/WebKit/Source/wtf/AddressSpaceRandomization.cpp
+++ b/third_party/WebKit/Source/wtf/AddressSpaceRandomization.cpp
@@ -108,6 +108,17 @@ void* getRandomPageBase()
     random &= 0x3fffffffffUL;
     random += 0x1000000000UL;
 #else // !CPU(X86_64) && !CPU(ARM64)
+#if OS(WIN)
+    // On win32 host systems the randomization plus huge alignment causes
+    // excessive fragmentation. Plus most of these systems lack ASLR, so the
+    // randomization isn't buying anything. In that case we just skip it.
+    // TODO(jschuh): Just dump the randomization when HE-ASLR is present.
+    static BOOL isWow64 = -1;
+    if (isWow64 == -1 && !IsWow64Process(GetCurrentProcess(), &isWow64))
+        isWow64 = FALSE;
+    if (!isWow64)
+        return nullptr;
+#endif // OS(WIN)
     // This is a good range on Windows, Linux and Mac.
     // Allocates in the 0.5-1.5GB region.
     random &= 0x3fffffff;