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

PRESUBMIT.py

Index: PRESUBMIT.py
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index 520642ea664fab16705f539995d8eebc408076bb..cd183fcd9182db21a8d759576eef69410dccc5c3 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -1312,6 +1312,40 @@ def _CheckJavaStyle(input_api, output_api):
       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)
@@ -1530,6 +1564,7 @@ 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