Fix obsolete gradle warnings #26544
Description
Currently the main flutter.gradle file contains a couple of deprecations that will throw warnings in Android Studio 3.3 with the latest gradle plugin.
WARNING: API 'variant.getMergeAssets()' is obsolete and has been replaced with 'variant.getMergeAssetsProvider()'.
It will be removed at the end of 2019.
For more information, see https://d.android.com/r/tools/task-configuration-avoidance.
REASON: Called from:<flutterpath>/packages/flutter_tools/gradle/flutter.gradle:394
WARNING: API 'variantOutput.getProcessResources()' is obsolete and has been replaced with 'variantOutput.getProcessResourcesProvider()'.
It will be removed at the end of 2019.
For more information, see https://d.android.com/r/tools/task-configuration-avoidance.
REASON: Called from: /<flutterpath>/packages/flutter_tools/gradle/flutter.gradle:406
Appropriate output from flutter doctor:
[✓] Flutter (Channel master, v1.1.10-pre.52, on Linux, locale en_US.UTF-8)
• Flutter version 1.1.10-pre.52 at /opt/google/flutter
• Framework revision d22cc77d27 (87 minutes ago), 2019-01-14 14:14:48 -0500
• Engine revision fea645b801
• Dart version 2.1.1 (build 2.1.1-dev.1.0 1c9eb3cef8)