Don't let "aapt crunch" increase image size.

For an image that's already optimized, aapt crunch typically increases
the image size. In this case, we now use the original image instead of
the crunched image. 9-patches, however, must always be crunched, since
crunching adds important metadata to the file.

Currently, this saves 50KB, but has the potential to save up to 300KB
once we optimize all the images in the codebase.

BUG=407781

Review URL: https://codereview.chromium.org/867483005

Cr-Commit-Position: refs/heads/master@{#313656}

build/android/gyp/process_resources.py

@@ -126,6 +126,36 @@ def CreateExtraRJavaFiles(r_dir, extra_packages):
     # affect how the code in this .apk target could refer to the resources.
 
 
+def CrunchDirectory(aapt, input_dir, output_dir):
+  """Crunches the images in input_dir and its subdirectories into output_dir.
+
+  If an image is already optimized, crunching often increases image size. In
+  this case, the crunched image is overwritten with the original image.
+  """
+  aapt_cmd = [aapt,
+              'crunch',
+              '-C', output_dir,
+              '-S', input_dir,
+              '--ignore-assets', build_utils.AAPT_IGNORE_PATTERN]
+  build_utils.CheckOutput(aapt_cmd, stderr_filter=FilterCrunchStderr,
+                          fail_func=DidCrunchFail)
+
+  # Check for images whose size increased during crunching and replace them
+  # with their originals (except for 9-patches, which must be crunched).
+  for dir_, _, files in os.walk(output_dir):
+    for crunched in files:
+      if crunched.endswith('.9.png'):
+        continue
+      if not crunched.endswith('.png'):
+        raise Exception('Unexpected file in crunched dir: ' + crunched)
+      crunched = os.path.join(dir_, crunched)
+      original = os.path.join(input_dir, os.path.relpath(crunched, output_dir))
+      original_size = os.path.getsize(original)
+      crunched_size = os.path.getsize(crunched)
+      if original_size < crunched_size:
+        shutil.copyfile(original, crunched)
+
+
 def FilterCrunchStderr(stderr):
   """Filters out lines from aapt crunch's stderr that can safely be ignored."""
   filtered_lines = []
@@ -260,17 +290,11 @@ def main():
     # Crunch image resources. This shrinks png files and is necessary for
     # 9-patch images to display correctly. 'aapt crunch' accepts only a single
     # directory at a time and deletes everything in the output directory.
-    for idx, d in enumerate(input_resource_dirs):
+    for idx, input_dir in enumerate(input_resource_dirs):
       crunch_dir = os.path.join(base_crunch_dir, str(idx))
       build_utils.MakeDirectory(crunch_dir)
       zip_resource_dirs.append(crunch_dir)
-      aapt_cmd = [aapt,
-                  'crunch',
-                  '-C', crunch_dir,
-                  '-S', d,
-                  '--ignore-assets', build_utils.AAPT_IGNORE_PATTERN]
-      build_utils.CheckOutput(aapt_cmd, stderr_filter=FilterCrunchStderr,
-                              fail_func=DidCrunchFail)
+      CrunchDirectory(aapt, input_dir, crunch_dir)
 
     ZipResources(zip_resource_dirs, options.resource_zip_out)