Android: Tint color inconsistency

issue に記載された Android slider の動作を再現するため、まず minimumTrackTintColor と maximumTrackTintColor に同じ値を設定してテストし、次に rgba の例をテストします。Android slider の実装と tint の処理を追跡します。Android による上書きや視覚的な変更なしに、両方の色が指定どおりに描画されれば完了です。

Environment

  React Native Environment Info:
    System:
      OS: macOS 10.14.5
      CPU: (8) x64 Intel(R) Core(TM) i7-4850HQ CPU @ 2.30GHz
      Memory: 1.16 GB / 16.00 GB
      Shell: 3.2.57 - /bin/bash
    Binaries:
      Node: 11.14.0 - ~/.nvm/versions/node/v11.14.0/bin/node
      Yarn: 1.15.2 - ~/.yarn/bin/yarn
      npm: 6.9.0 - ~/.nvm/versions/node/v11.14.0/bin/npm
      Watchman: 3.9.0 - /usr/local/bin/watchman
    SDKs:
      iOS SDK:
        Platforms: iOS 12.2, macOS 10.14, tvOS 12.2, watchOS 5.2
      Android SDK:
        API Levels: 23, 24, 25, 26, 27, 28
        Build Tools: 23.0.1, 23.0.2, 23.0.3, 24.0.0, 25.0.0, 25.0.1, 25.0.2, 25.0.3, 26.0.1, 26.0.2, 26.0.3, 27.0.1, 27.0.2, 27.0.3, 28.0.3
        System Images: android-19 | Google APIs Intel x86 Atom, android-23 | Google APIs Intel x86 Atom, android-24 | Google APIs Intel x86 Atom, android-25 | Google Play Intel x86 Atom, android-26 | Google APIs Intel x86 Atom, android-26 | Google Play Intel x86 Atom, android-27 | Google APIs Intel x86 Atom, android-27 | Google Play Intel x86 Atom, android-28 | Google Play Intel x86 Atom
    IDEs:
      Android Studio: 3.4 AI-183.6156.11.34.5522156
      Xcode: 10.2.1/10E1001 - /usr/bin/xcodebuild
    npmPackages:
      react: 16.8.3 => 16.8.3
      react-native: 0.59.8 => 0.59.8
    npmGlobalPackages:
      react-native-cli: 2.0.1
      react-native-git-upgrade: 0.2.7

Description

When maximumTintColor matches minimumTintColor, Android overrides the colour setting and makes maximumTintColor lighter than minimumTintColor.

Also, something like below will be ignored as it appears that Android likes to paint a more visible shade on the minimum side.

{ minimumTrackTintColor: 'rgba(255,255,255,0.1)', maximumTrackTintColor: 'rgba(255,255,255,0.4)' }