build: Add android_debug_resources_temp_dir

Normally, compiling Android resources requires unpacking
and processing resource dependencies into a temporary
directory before sending the result to 'aapt2 compile',
then getting rid of these intermediate files.

To help debug issues related to Android resource compilation,
this CL introduces a new GN variable that can be set in your
args.gn, to force the build to put all such build directories
under a top-level directory, and not removing intermediate
files in it.

This should allow inspecting the intermediate files to better
understand what's going on.

This is needed to debug issues that appeared in my attempt
to change the resources stored in APKs versus bundles, e.g.:
https://chromium-review.googlesource.com/c/chromium/src/+/1270947

BUG=879228,882860,897056
R=agrieve@chromium.org, estevenson@chromium.org,yfriedman@chromium.org

Change-Id: I76c79a893b0bbdb56ba685f4304da929d11c7e05
Reviewed-on: https://chromium-review.googlesource.com/c/1288436Reviewed-by: agrieve <agrieve@chromium.org>
Commit-Queue: David Turner <digit@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601178}

build/android/gyp/compile_resources.py

@@ -27,6 +27,11 @@ from xml.etree import ElementTree
 from util import build_utils
 from util import resource_utils
 
+# Name of environment variable that can be used to force this script to
+# put temporary resource files into specific sub-directories, instead of
+# temporary ones.
+_ENV_DEBUG_VARIABLE = 'ANDROID_DEBUG_TEMP_RESOURCES_DIR'
+
 # Import jinja2 from third_party/jinja2
 sys.path.insert(1, os.path.join(build_utils.DIR_SOURCE_ROOT, 'third_party'))
 from jinja2 import Template # pylint: disable=F0401
@@ -581,8 +586,8 @@ def _WriteFinalRTxtFile(options, aapt_r_txt_path):
   return r_txt_file
 
 
-def _OnStaleMd5(options):
-  with resource_utils.BuildContext() as build:
+def _OnStaleMd5(options, debug_temp_resources_dir):
+  with resource_utils.BuildContext(debug_temp_resources_dir) as build:
     dep_subdirs = resource_utils.ExtractDeps(options.dependencies_res_zips,
                                              build.deps_dir)
 
@@ -657,10 +662,17 @@ def main(args):
 
   input_strings.extend(_CreateLinkApkArgs(options))
 
+  debug_temp_resources_dir = os.environ.get(_ENV_DEBUG_VARIABLE)
+  if debug_temp_resources_dir:
+    build_utils.DeleteDirectory(debug_temp_resources_dir)
+    build_utils.MakeDirectory(debug_temp_resources_dir)
+
+
   possible_input_paths = [
     options.aapt_path,
     options.aapt2_path,
     options.android_manifest,
+    debug_temp_resources_dir,
     options.shared_resources_whitelist,
   ]
   possible_input_paths += options.include_resources
@@ -672,7 +684,7 @@ def main(args):
     input_paths.append(options.webp_binary)
 
   build_utils.CallAndWriteDepfileIfStale(
-      lambda: _OnStaleMd5(options),
+      lambda: _OnStaleMd5(options, debug_temp_resources_dir),
       options,
       input_paths=input_paths,
       input_strings=input_strings,

build/android/gyp/util/resource_utils.py

@@ -407,11 +407,22 @@ def ExtractDeps(dep_zips, deps_dir):
 
 
 class _ResourceBuildContext(object):
-  """A temporary directory for packaging and compiling Android resources."""
-  def __init__(self):
+  """A temporary directory for packaging and compiling Android resources.
+
+  Args:
+    temp_dir: Optional root build directory path. If None, a temporary
+      directory will be created, and removed in Close().
+  """
+  def __init__(self, temp_dir=None):
     """Initialized the context."""
     # The top-level temporary directory.
-    self.temp_dir = tempfile.mkdtemp()
+    if temp_dir:
+      self.temp_dir = temp_dir
+      self.remove_on_exit = False
+    else:
+      self.temp_dir = tempfile.mkdtemp()
+      self.remove_on_exit = True
+
     # A location to store resources extracted form dependency zip files.
     self.deps_dir = os.path.join(self.temp_dir, 'deps')
     os.mkdir(self.deps_dir)
@@ -426,14 +437,15 @@ class _ResourceBuildContext(object):
 
   def Close(self):
     """Close the context and destroy all temporary files."""
-    shutil.rmtree(self.temp_dir)
+    if self.remove_on_exit:
+      shutil.rmtree(self.temp_dir)
 
 
 @contextlib.contextmanager
-def BuildContext():
+def BuildContext(temp_dir=None):
   """Generator for a _ResourceBuildContext instance."""
   try:
-    context = _ResourceBuildContext()
+    context = _ResourceBuildContext(temp_dir)
     yield context
   finally:
     context.Close()