Revert of Don't bother running realpath in DeviceUtils._GetChangedAndStaleFiles()

build/android/pylib/device/device_utils.py

Index: build/android/pylib/device/device_utils.py
diff --git a/build/android/pylib/device/device_utils.py b/build/android/pylib/device/device_utils.py
index 976399cfa35fa1222f4243b0076870b5ffc4585a..292c60533617888108ed379496824fb8c0eadfbb 100644
--- a/build/android/pylib/device/device_utils.py
+++ b/build/android/pylib/device/device_utils.py
@@ -1039,12 +1039,21 @@ class DeviceUtils(object):
       3rd element: a list of stale files under device_path, or [] when
         track_stale == False
     """
+    real_host_path = os.path.realpath(host_path)
     try:
-      host_checksums = md5sum.CalculateHostMd5Sums([host_path])
-      interesting_device_paths = [device_path]
-      if not track_stale and os.path.isdir(host_path):
+      real_device_path = self.RunShellCommand(
+          ['realpath', device_path], single_line=True, check_return=True)
+    except device_errors.CommandFailedError:
+      real_device_path = None
+    if not real_device_path:
+      return ([(host_path, device_path)], [], [])
+
+    try:
+      host_checksums = md5sum.CalculateHostMd5Sums([real_host_path])
+      interesting_device_paths = [real_device_path]
+      if not track_stale and os.path.isdir(real_host_path):
         interesting_device_paths = [
-            posixpath.join(device_path, os.path.relpath(p, host_path))
+            posixpath.join(real_device_path, os.path.relpath(p, real_host_path))
             for p in host_checksums.keys()]
       device_checksums = md5sum.CalculateDeviceMd5Sums(
           interesting_device_paths, self)
@@ -1056,8 +1065,8 @@ class DeviceUtils(object):
     up_to_date = []
     to_delete = []
     if os.path.isfile(host_path):
-      host_checksum = host_checksums.get(host_path)
-      device_checksum = device_checksums.get(device_path)
+      host_checksum = host_checksums.get(real_host_path)
+      device_checksum = device_checksums.get(real_device_path)
       if host_checksum == device_checksum:
         up_to_date.append(host_path)
       else:
@@ -1065,7 +1074,7 @@ class DeviceUtils(object):
     else:
       for host_abs_path, host_checksum in host_checksums.iteritems():
         device_abs_path = posixpath.join(
-            device_path, os.path.relpath(host_abs_path, host_path))
+            real_device_path, os.path.relpath(host_abs_path, real_host_path))
         device_checksum = device_checksums.pop(device_abs_path, None)
         if device_checksum == host_checksum:
           up_to_date.append(host_abs_path)