Don't trigger HW acceleration from Toasts on low-end devices.

PRESUBMIT.py

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Top-level presubmit script for Chromium.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details about the presubmit API built into depot_tools.
 """
 
@@ skipping 1294 matching lines @@
     import checkstyle
   finally:
     # Restore sys.path to what it was before.
     sys.path = original_sys_path
 
   return checkstyle.RunCheckstyle(
       input_api, output_api, 'tools/android/checkstyle/chromium-style-5.0.xml',
       black_list=_EXCLUDED_PATHS + input_api.DEFAULT_BLACK_LIST)
 
 
+def _CheckAndroidToastUsage(input_api, output_api):
+  """Checks that Chromium code uses org.chromium.ui.widget.Toast
+     instead of android.widget.Toast (Chromium Toast doesn't force hardware
+     acceleration on low-end devices, saving memory).
+  """
+  toast_import_pattern = input_api.re.compile(
+      r'^import android\.widget\.Toast;$')
+
+  import_errors = []
+
+  sources = lambda x: input_api.FilterSourceFile(x, white_list=(r'.*\.java$',))
+  for f in input_api.AffectedSourceFiles(sources):
+    for line_num, line in f.ChangedContents():
+      if toast_import_pattern.search(line):
+        import_errors.append("%s:%d" % (f.LocalPath(), line_num))
+
+  results = []
+  if import_errors:
+    results.append(output_api.PresubmitPromptWarning(
+        '"android.widget.Toast" usage is detected. Android toasts use hardware'

[Dmitry Skiba, 2015/08/11 23:49:50]

Example output:

** Presubmit Warnings **
"android.widget.Toast" usage is detected. Android toasts use hardware
acceleration, and can be
costly on low-end devices. If your code triggers toasts on low-end devices
(especially during
normal browsing workflow), you should use "org.chromium.ui.widget.Toast"
instead.
You don't need to bother if toast is shown only from an activity that is
hardware accelerated
(e.g. Preferences) or the one that is not visible to the end user (e.g.
ChromeShellActivity).
In any case, feel free to contact dskiba@chromium.org if you have any questions
or concerns.
 
chrome/android/javatests/src/org/chromium/chrome/browser/hardware_acceleration/Utils.java:9

+        ' acceleration, and can be\ncostly on low-end devices. If your code'
+        ' triggers toasts on low-end devices (especially during\nnormal'
+        ' browsing workflow), you should use "org.chromium.ui.widget.Toast"'
+        ' instead.\n'
+        "You don't need to bother if toast is shown only from an activity that"
+        ' is hardware accelerated\n(e.g. Preferences) or the one that is not'
+        ' visible to the end user (e.g. ChromeShellActivity).\n'
+        'In any case, feel free to contact dskiba@chromium.org if you have any'
+        ' questions or concerns.',
+        import_errors))
+
+  return results
+
+
 def _CheckAndroidCrLogUsage(input_api, output_api):
   """Checks that new logs using org.chromium.base.Log:
     - Are using 'TAG' as variable name for the tags (warn)
     - Are using the suggested name format for the tags: "cr.<PackageTag>" (warn)
     - Are using a tag that is shorter than 23 characters (error)
   """
   cr_log_import_pattern = input_api.re.compile(
       r'^import org\.chromium\.base\.Log;$', input_api.re.MULTILINE)
   class_in_base_pattern = input_api.re.compile(
       r'^package org\.chromium\.base;$', input_api.re.MULTILINE)
@@ skipping 198 matching lines @@
           results.append(output_api.PresubmitError(
               "%s:%d: Use of deprecated JS %s, use %s instead" %
               (fpath.LocalPath(), lnum, deprecated, replacement)))
   return results
 
 
 def _AndroidSpecificOnUploadChecks(input_api, output_api):
   """Groups checks that target android code."""
   results = []
   results.extend(_CheckAndroidCrLogUsage(input_api, output_api))
+  results.extend(_CheckAndroidToastUsage(input_api, output_api))
   return results
 
 
 def _CommonChecks(input_api, output_api):
   """Checks common to both upload and commit."""
   results = []
   results.extend(input_api.canned_checks.PanProjectChecks(
       input_api, output_api,
       excluded_paths=_EXCLUDED_PATHS + _TESTRUNNER_PATHS))
   results.extend(_CheckAuthorizedAuthor(input_api, output_api))
@@ skipping 339 matching lines @@
   for master in masters:
     try_config.setdefault(master, {})
     for builder in masters[master]:
       # Do not trigger presubmit builders, since they're likely to fail
       # (e.g. OWNERS checks before finished code review), and we're
       # running local presubmit anyway.
       if 'presubmit' not in builder:
         try_config[master][builder] = ['defaulttests']
 
   return try_config