Add instance-level in-memory cache for PushIfNeeded().

build/android/pylib/android_commands.py

Index: build/android/pylib/android_commands.py
diff --git a/build/android/pylib/android_commands.py b/build/android/pylib/android_commands.py
index 8d8949cac74c8db343ff68b5c9a33da11d462bf8..d17a3f856fee5d57f0f08dc58b1a7ac83c144625 100644
--- a/build/android/pylib/android_commands.py
+++ b/build/android/pylib/android_commands.py
@@ -253,6 +253,7 @@ class AndroidCommands(object):
     self._actual_push_size = 0
     self._external_storage = ''
     self._util_wrapper = ''
+    self._push_if_needed_cache = {}
 
   def _LogShell(self, cmd):
     """Logs the adb shell command."""
@@ -917,6 +918,15 @@ class AndroidCommands(object):
     MAX_INDIVIDUAL_PUSHES = 50
     assert os.path.exists(host_path), 'Local path not found %s' % host_path
 
+    # See if the file on the host changed since the last push (if any) and
+    # return early if it didn't. Note that this shortcut assumes that the tests
+    # on the device don't modify the files.
+    if not os.path.isdir(host_path):
+      if host_path in self._push_if_needed_cache:
+        host_path_mtime = self._push_if_needed_cache[host_path]
+        if host_path_mtime == os.stat(host_path).st_mtime:
+          return
+
     def GetHostSize(path):
       return int(cmd_helper.GetCmdOutput(['du', '-sb', path]).split()[0])
 
@@ -941,6 +951,8 @@ class AndroidCommands(object):
       while True:
         output = self._adb.SendCommand(push_command, timeout_time=30 * 60)
         if _HasAdbPushSucceeded(output):
+          if not os.path.isdir(host_path):

[craigdh, 2013/12/10 19:23:32]

If we're only doing this for single files, then instead of doing this in the
loop (calling os.path.isdir for every file when we're pushing large directories)
just stick it at the end of PushIfNeeded (line 980). An exception is raised if
the push fails so this will only be cached if the file is successfully pushed.

+            self._push_if_needed_cache[host] = os.stat(host).st_mtime
           return
         if retry < 3:
           retry += 1