diff --git a/python/mozbuild/mozpack/files.py b/python/mozbuild/mozpack/files.py
index 5c7b21cc903..f7e578c5c82 100644
--- a/python/mozbuild/mozpack/files.py
+++ b/python/mozbuild/mozpack/files.py
@@ -2,9 +2,12 @@
 # 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/.
 
+import errno
 import os
 import re
 import shutil
+import stat
+import uuid
 from mozpack.executables import (
     is_executable,
     may_strip,
@@ -159,6 +162,100 @@ class ExecutableFile(File):
         return True
 
 
+class AbsoluteSymlinkFile(File):
+    '''File class that is copied by symlinking (if available).
+
+    This class only works if the target path is absolute.
+    '''
+
+    def __init__(self, path):
+        if not os.path.isabs(path):
+            raise ValueError('Symlink target not absolute: %s' % path)
+
+        File.__init__(self, path)
+
+    def copy(self, dest, skip_if_older=True):
+        assert isinstance(dest, basestring)
+
+        # The logic in this function is complicated by the fact that symlinks
+        # aren't universally supported. So, where symlinks aren't supported, we
+        # fall back to file copying. Keep in mind that symlink support is
+        # per-filesystem, not per-OS.
+
+        # Handle the simple case where symlinks are definitely not supported by
+        # falling back to file copy.
+        if not hasattr(os, 'symlink'):
+            return File.copy(self, dest, skip_if_older=skip_if_older)
+
+        # Always verify the symlink target path exists.
+        if not os.path.exists(self.path):
+            raise ErrorMessage('Symlink target path does not exist: %s' % self.path)
+
+        st = None
+
+        try:
+            st = os.lstat(dest)
+        except OSError as ose:
+            if ose.errno != errno.ENOENT:
+                raise
+
+        # If the dest is a symlink pointing to us, we have nothing to do.
+        # If it's the wrong symlink, the filesystem must support symlinks,
+        # so we replace with a proper symlink.
+        if st and stat.S_ISLNK(st.st_mode):
+            link = os.readlink(dest)
+            if link == self.path:
+                return False
+
+            os.remove(dest)
+            os.symlink(self.path, dest)
+            return True
+
+        # If the destination doesn't exist, we try to create a symlink. If that
+        # fails, we fall back to copy code.
+        if not st:
+            try:
+                os.symlink(self.path, dest)
+                return True
+            except OSError:
+                return File.copy(self, dest, skip_if_older=skip_if_older)
+
+        # Now the complicated part. If the destination exists, we could be
+        # replacing a file with a symlink. Or, the filesystem may not support
+        # symlinks. We want to minimize I/O overhead for performance reasons,
+        # so we keep the existing destination file around as long as possible.
+        # A lot of the system calls would be eliminated if we cached whether
+        # symlinks are supported. However, even if we performed a single
+        # up-front test of whether the root of the destination directory
+        # supports symlinks, there's no guarantee that all operations for that
+        # dest (or source) would be on the same filesystem and would support
+        # symlinks.
+        #
+        # Our strategy is to attempt to create a new symlink with a random
+        # name. If that fails, we fall back to copy mode. If that works, we
+        # remove the old destination and move the newly-created symlink into
+        # its place.
+
+        temp_dest = os.path.join(os.path.dirname(dest), str(uuid.uuid4()))
+        try:
+            os.symlink(self.path, temp_dest)
+        # TODO Figure out exactly how symlink creation fails and only trap
+        # that.
+        except EnvironmentError:
+            return File.copy(self, dest, skip_if_older=skip_if_older)
+
+        # If removing the original file fails, don't forget to clean up the
+        # temporary symlink.
+        try:
+            os.remove(dest)
+        except EnvironmentError:
+            os.remove(temp_dest)
+            raise
+
+        os.rename(temp_dest, dest)
+        return True
+
+
 class GeneratedFile(BaseFile):
     '''
     File class for content with no previous existence on the filesystem.
diff --git a/python/mozbuild/mozpack/test/test_files.py b/python/mozbuild/mozpack/test/test_files.py
index ad6d9e8722b..9af482f63c0 100644
--- a/python/mozbuild/mozpack/test/test_files.py
+++ b/python/mozbuild/mozpack/test/test_files.py
@@ -3,6 +3,7 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 from mozpack.files import (
+    AbsoluteSymlinkFile,
     Dest,
     File,
     GeneratedFile,
@@ -216,6 +217,112 @@ class TestFile(TestWithTmpDir):
         self.assertEqual('fooo', open(dest, 'rb').read())
 
 
+class TestAbsoluteSymlinkFile(TestWithTmpDir):
+    def setUp(self):
+        TestWithTmpDir.setUp(self)
+
+        self.symlink_supported = False
+
+        if not hasattr(os, 'symlink'):
+            return
+
+        dummy_path = self.tmppath('dummy_file')
+        with open(dummy_path, 'a'):
+            pass
+
+        try:
+            os.symlink(dummy_path, self.tmppath('dummy_symlink'))
+            os.remove(self.tmppath('dummy_symlink'))
+        except EnvironmentError:
+            pass
+        finally:
+            os.remove(dummy_path)
+
+    def test_absolute_relative(self):
+        AbsoluteSymlinkFile('/foo')
+
+        with self.assertRaisesRegexp(ValueError, 'Symlink target not absolute'):
+            AbsoluteSymlinkFile('./foo')
+
+    def test_symlink_file(self):
+        source = self.tmppath('test_path')
+        with open(source, 'wt') as fh:
+            fh.write('Hello world')
+
+        s = AbsoluteSymlinkFile(source)
+        dest = self.tmppath('symlink')
+        self.assertTrue(s.copy(dest))
+
+        if self.symlink_supported:
+            self.assertTrue(os.path.islink(dest))
+            link = os.readlink(dest)
+            self.assertEqual(link, source)
+        else:
+            self.assertTrue(os.path.isfile(dest))
+            content = open(dest).read()
+            self.assertEqual(content, 'Hello world')
+
+    def test_replace_file_with_symlink(self):
+        # If symlinks are supported, an existing file should be replaced by a
+        # symlink.
+        source = self.tmppath('test_path')
+        with open(source, 'wt') as fh:
+            fh.write('source')
+
+        dest = self.tmppath('dest')
+        with open(dest, 'a'):
+            pass
+
+        s = AbsoluteSymlinkFile(source)
+        s.copy(dest, skip_if_older=False)
+
+        if self.symlink_supported:
+            self.assertTrue(os.path.islink(dest))
+            link = os.readlink(dest)
+            self.assertEqual(link, source)
+        else:
+            self.assertTrue(os.path.isfile(dest))
+            content = open(dest).read()
+            self.assertEqual(content, 'source')
+
+    def test_replace_symlink(self):
+        if not self.symlink_supported:
+            return
+
+        source= self.tmppath('source')
+        dest = self.tmppath('dest')
+
+        os.symlink(self.tmppath('bad'), dest)
+        self.assertTrue(os.path.islink(dest))
+
+        s = AbsoluteSymlinkFile(source)
+        self.assertTrue(s.copy(dest))
+
+        self.assertTrue(os.path.islink(dest))
+        link = os.readlink(dest)
+        self.assertEqual(link, source)
+
+    def test_noop(self):
+        if not hasattr(os, 'symlink'):
+            return
+
+        source = self.tmppath('source')
+        dest = self.tmppath('dest')
+
+        with open(source, 'a'):
+            pass
+
+        os.symlink(source, dest)
+        link = os.readlink(dest)
+        self.assertEqual(link, source)
+
+        s = AbsoluteSymlinkFile(source)
+        self.assertFalse(s.copy(dest))
+
+        link = os.readlink(dest)
+        self.assertEqual(link, source)
+
+
 class TestGeneratedFile(TestWithTmpDir):
     def test_generated_file(self):
         '''