diff -r 000000000000 -r 6474c204b198 xpcom/base/nsUUIDGenerator.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xpcom/base/nsUUIDGenerator.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,160 @@
+/* -*- Mode: C++; tab-width: 50; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#if defined(XP_WIN)
+#include <windows.h>
+#include <objbase.h>
+#elif defined(XP_MACOSX)
+#include <CoreFoundation/CoreFoundation.h>
+#else
+#include <stdlib.h>
+#include "prrng.h"
+#endif
+
+#include "nsUUIDGenerator.h"
+
+using namespace mozilla;
+
+NS_IMPL_ISUPPORTS(nsUUIDGenerator, nsIUUIDGenerator)
+
+nsUUIDGenerator::nsUUIDGenerator()
+    : mLock("nsUUIDGenerator.mLock")
+{
+}
+
+nsUUIDGenerator::~nsUUIDGenerator()
+{
+}
+
+nsresult
+nsUUIDGenerator::Init()
+{
+    // We're a service, so we're guaranteed that Init() is not going
+    // to be reentered while we're inside Init().
+    
+#if !defined(XP_WIN) && !defined(XP_MACOSX) && !defined(ANDROID)
+    /* initialize random number generator using NSPR random noise */
+    unsigned int seed;
+
+    size_t bytes = 0;
+    while (bytes < sizeof(seed)) {
+        size_t nbytes = PR_GetRandomNoise(((unsigned char *)&seed)+bytes,
+                                          sizeof(seed)-bytes);
+        if (nbytes == 0) {
+            return NS_ERROR_FAILURE;
+        }
+        bytes += nbytes;
+    }
+
+    /* Initialize a new RNG state, and immediately switch
+     * back to the previous one -- we want to use mState
+     * only for our own calls to random().
+     */
+    mSavedState = initstate(seed, mState, sizeof(mState));
+    setstate(mSavedState);
+
+    mRBytes = 4;
+#ifdef RAND_MAX
+    if ((unsigned long) RAND_MAX < (unsigned long)0xffffffff)
+        mRBytes = 3;
+    if ((unsigned long) RAND_MAX < (unsigned long)0x00ffffff)
+        mRBytes = 2;
+    if ((unsigned long) RAND_MAX < (unsigned long)0x0000ffff)
+        mRBytes = 1;
+    if ((unsigned long) RAND_MAX < (unsigned long)0x000000ff)
+        return NS_ERROR_FAILURE;
+#endif
+
+#endif /* non XP_WIN and non XP_MACOSX */
+
+    return NS_OK;
+}
+
+NS_IMETHODIMP
+nsUUIDGenerator::GenerateUUID(nsID** ret)
+{
+    nsID *id = static_cast<nsID*>(NS_Alloc(sizeof(nsID)));
+    if (id == nullptr)
+        return NS_ERROR_OUT_OF_MEMORY;
+
+    nsresult rv = GenerateUUIDInPlace(id);
+    if (NS_FAILED(rv)) {
+        NS_Free(id);
+        return rv;
+    }
+
+    *ret = id;
+    return rv;
+}
+
+NS_IMETHODIMP
+nsUUIDGenerator::GenerateUUIDInPlace(nsID* id)
+{
+    // The various code in this method is probably not threadsafe, so lock
+    // across the whole method.
+    MutexAutoLock lock(mLock);
+
+#if defined(XP_WIN)
+    HRESULT hr = CoCreateGuid((GUID*)id);
+    if (FAILED(hr))
+        return NS_ERROR_FAILURE;
+#elif defined(XP_MACOSX)
+    CFUUIDRef uuid = CFUUIDCreate(kCFAllocatorDefault);
+    if (!uuid)
+        return NS_ERROR_FAILURE;
+
+    CFUUIDBytes bytes = CFUUIDGetUUIDBytes(uuid);
+    memcpy(id, &bytes, sizeof(nsID));
+
+    CFRelease(uuid);
+#else /* not windows or OS X; generate randomness using random(). */
+    /* XXX we should be saving the return of setstate here and switching
+     * back to it; instead, we use the value returned when we called
+     * initstate, since older glibc's have broken setstate() return values
+     */
+#ifndef ANDROID
+    setstate(mState);
+#endif
+
+    size_t bytesLeft = sizeof(nsID);
+    while (bytesLeft > 0) {
+#ifdef ANDROID
+        long rval = arc4random();
+        const size_t mRBytes = 4;
+#else
+        long rval = random();
+#endif
+
+
+        uint8_t *src = (uint8_t*)&rval;
+        // We want to grab the mRBytes least significant bytes of rval, since
+        // mRBytes less than sizeof(rval) means the high bytes are 0.
+#ifdef IS_BIG_ENDIAN
+        src += sizeof(rval) - mRBytes;
+#endif
+        uint8_t *dst = ((uint8_t*) id) + (sizeof(nsID) - bytesLeft);
+        size_t toWrite = (bytesLeft < mRBytes ? bytesLeft : mRBytes);
+        for (size_t i = 0; i < toWrite; i++)
+            dst[i] = src[i];
+
+        bytesLeft -= toWrite;
+    }
+
+    /* Put in the version */
+    id->m2 &= 0x0fff;
+    id->m2 |= 0x4000;
+
+    /* Put in the variant */
+    id->m3[0] &= 0x3f;
+    id->m3[0] |= 0x80;
+
+#ifndef ANDROID
+    /* Restore the previous RNG state */
+    setstate(mSavedState);
+#endif
+#endif
+
+    return NS_OK;
+}