Work around Xcode 9 debug actool message.

build/toolchain/mac/compile_xcassets.py

Index: build/toolchain/mac/compile_xcassets.py
diff --git a/build/toolchain/mac/compile_xcassets.py b/build/toolchain/mac/compile_xcassets.py
index ac0742eb56f7800656b3f229681b14ae0baaa531..9b4110063140a1a6341f83bd69267efdca487703 100644
--- a/build/toolchain/mac/compile_xcassets.py
+++ b/build/toolchain/mac/compile_xcassets.py
@@ -55,13 +55,25 @@ def CompileXCAssets(
   #
   # Ignore any lines in the output matching those (last line is an empty line)
   # and consider that the build failed if the output contains any other lines.
+  #
+  # crbug.com/730054 Xcode 9's beta introduced a CoreUI(DEBUG) message followed
+  # by a detail message that can be ignored.  Presumably this will be removed
+  # once Xcode 9 GMs.
+  skip_next = False
   for line in stdout.splitlines():
+    if skip_next:
+      skip_next = False

[sdefresne, 2017/06/06 16:49:02]

It looks like the next line is

2017-06-06 10:42:25.690 IBCocoaTouchImageCatalogTool[4246:24111] RPC shutdown
with error: Error Domain=IBMessageChannelErrorDomain Code=4 "Failed to
communicate with Interface Builder" UserInfo={NSLocalizedDescription=Failed to
communicate with Interface Builder, NSLocalizedFailureReason=The agent crashed}

which look like the issue we had when using different versions of actool.

Can we add a separate check for that line, something like the following:

  if line.contains("Error Domain=IBMessageChannelErrorDomain Code=4"):
    continue

And update the comment (I think this is independent of Xcode 9 GM).

[justincohen, 2017/06/06 17:26:00]

Are you sure we want to do this?  I have no idea if
IBMessageChannelErrorDomain/4 is something we can always ignore, or just ignore
after a Debug message?  

If you do, then I'll remove all the skip_next logic.

When we had the error before, did we still have 
com.apple.actool.compilation-results?  I wonder if we should just make sure 
com.apple.actool.compilation-results exists and ignore everything else?

[rohitrao (ping after 24h), 2017/06/06 18:09:46]

I'd like to scope this as tightly to the actual error message we're seeing as
possible.  We may have to ignore more things in the future, but at least we'll
get loud errors when something unexpected pops up.

[justincohen, 2017/06/06 20:03:04]

Done.

+      continue
     if not line:
       continue
     if line == '/* com.apple.actool.compilation-results */':
       continue
     if line == os.path.abspath(output):
       continue
+    if line.startswith('CoreUI(DEBUG)'):
+      skip_next = True
+      continue
+    print line

[sdefresne, 2017/06/06 16:49:02]

I think this "print line" is debug and need to be removed.

[justincohen, 2017/06/06 17:26:00]

oops, thanks!

     sys.stderr.write(stdout)
     sys.exit(1)