Make PushIfNeeded do what is says.

build/android/pylib/android_commands.py

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Provides an interface to communicate with the device via the adb command.
 
 Assumes adb binary is currently on system path.
 """
 
 import collections
@@ skipping 823 matching lines @@
       host_path: Path (file or directory) on the host.
       device_path: Path on the device.
       ignore_filenames: If True only the file contents are considered when
           checking whether a file has changed, otherwise the relative path
           must also match.
 
     Returns:
       A list of tuples of the form (host_path, device_path) for files whose
       md5sums do not match.
     """
+
+    # Md5Sum resolves symbolic links in path names so the calculation of
+    # relative path names from its output will need the real path names of the
+    # base directories. Having calculated these they are used throughout the
+    # function since this makes us less subject to any future changes to Md5Sum.
+    real_host_path = os.path.realpath(host_path)
+    real_device_path = self.RunShellCommand('realpath "%s"' % device_path)[0]
+
     host_hash_tuples, device_hash_tuples = self._RunMd5Sum(
-        host_path, device_path)
+        real_host_path, real_device_path)
 
     # Ignore extra files on the device.
     if not ignore_filenames:
       host_files = [os.path.relpath(os.path.normpath(p.path),
-                    os.path.normpath(host_path)) for p in host_hash_tuples]
+                                    real_host_path) for p in host_hash_tuples]
 
       def HostHas(fname):
         return any(path in fname for path in host_files)
 
       device_hash_tuples = [h for h in device_hash_tuples if HostHas(h.path)]
 
     if len(host_hash_tuples) > len(device_hash_tuples):
       logging.info('%s files do not exist on the device' %
                    (len(host_hash_tuples) - len(device_hash_tuples)))
 
     # Constructs the target device path from a given host path. Don't use when
     # only a single file is given as the base name given in device_path may
     # differ from that in host_path.
     def HostToDevicePath(host_file_path):
-      return os.path.join(device_path, os.path.relpath(
-          host_file_path, os.path.normpath(host_path)))
+      return os.path.join(device_path, os.path.relpath(host_file_path,
+                                                       real_host_path))
 
     device_hashes = [h.hash for h in device_hash_tuples]
-    return [(t.path, HostToDevicePath(t.path) if os.path.isdir(host_path) else
-             device_path)
+    return [(t.path, HostToDevicePath(t.path) if
+             os.path.isdir(real_host_path) else real_device_path)
             for t in host_hash_tuples if t.hash not in device_hashes]
 
   def PushIfNeeded(self, host_path, device_path):
     """Pushes |host_path| to |device_path|.
 
     Works for files and directories. This method skips copying any paths in
     |test_data_paths| that already exist on the device with the same hash.
 
     All pushed files can be removed by calling RemovePushedFiles().
     """
@@ skipping 773 matching lines @@
   """
   def __init__(self, output):
     self._output = output
 
   def write(self, data):
     data = data.replace('\r\r\n', '\n')
     self._output.write(data)
 
   def flush(self):
     self._output.flush()