Add modified time checking to strip_library_for_apk.py

build/android/gyp/util/build_utils.py

Index: build/android/gyp/util/build_utils.py
diff --git a/build/android/gyp/util/build_utils.py b/build/android/gyp/util/build_utils.py
index bdfa28aa8a5cd9c9f18d46c03060ab46361913e6..0b1e069ef6a54520ac4a5fdba2340cbecd444bef 100644
--- a/build/android/gyp/util/build_utils.py
+++ b/build/android/gyp/util/build_utils.py
@@ -101,3 +101,18 @@ def CheckCallDie(args, suppress_output=False, cwd=None):
       print stdout,
     return stdout
 
+
+def GetModifiedTime(path):
+ # For a symlink, the modified time should be the greater of the link's

[newt (away), 2013/04/04 02:18:49]

indent 2

[cjhopman, 2013/04/05 17:42:24]

Done.

+ # modified time and the modified time of the target.

[newt (away), 2013/04/04 02:18:49]

why?

[newt (away), 2013/04/04 22:52:06]

this can't hurt, but I can't think of a situation where the build would create a
symlink to an old file that hasn't been rebuilt.

[cjhopman, 2013/04/05 17:42:24]

Why need symlink time:
The case that I think could actually happen is that the target of a symlink
changes. I.e. I change a build action from creating a symlink pointing to
AndroidManifest1.xml to one pointing at AndroidManifest2.xml. In this case the
symlink modified time could be much more recent than the target modified time.

Why need target time:
If I depend on AndroidManifest.xml via AndroidManifestLink.xml, then modifying
AndroidManifest.xml should trigger me. This could particularly happen when the
symlink is not created by the build system (because if it were, it should be
touched by whatever build action creates it).

+ return max(os.lstat(path).st_mtime, os.stat(path).st_mtime)
+
+
+def IsTimeStale(output, inputs):
+  if not os.path.exists(output):
+    return True
+
+  output_time = GetModifiedTime(output)
+  input_time = max(map(GetModifiedTime, inputs))

[newt (away), 2013/04/04 02:18:49]

functional programming FTW :)

in practice, if inputs is a long list, this could be sped up by exiting early:

for input in inputs:
  if GetModifiedTime(input) > output_time:
    return True
return False

(not sure if you can dream up a functional way to do this...)

[cjhopman, 2013/04/05 17:42:24]

This works for me. 
This is very close:
return reduce(lambda stale, input: stale or GetModifiedTime(input) >
output_time, inputs, False)

To get true early exit, you pretty much have to deal with continuations and then
it becomes a real mess.

+
+  return output_time < input_time