Initial memory leak case study. (#1063)

* Initial memory leak case study.

* Code cleanup.

* More more leak added.

Author: terrylucas

case_study/memory_leak/.gitignore

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+.DS_Store
+.atom/
+.idea
+.packages
+.pub/
+build/
+ios/.generated/
+packages
+pubspec.lock
+.flutter-plugins

case_study/memory_leak/README.md

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+# Using Tab Bar
+
+A material design widget that displays a horizontal row of tabs.
+
+Read [[Documentation](https://docs.flutter.io/flutter/material/TabBar-class.html)] [[Material Design Spec](https://material.io/guidelines/components/tabs.html)]
+
+<img src="demo_img.gif" height="600em" />
+
+
+## Getting Started
+
+For help getting started with Flutter, view online [documentation](http://flutter.io/).

case_study/memory_leak/android/.gitignore

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+*.iml
+.gradle
+/local.properties
+/.idea/workspace.xml
+/.idea/libraries
+.DS_Store
+/build
+/captures
+GeneratedPluginRegistrant.java

case_study/memory_leak/android/app/build.gradle

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+def localProperties = new Properties()
+def localPropertiesFile = rootProject.file('local.properties')
+if (localPropertiesFile.exists()) {
+    localPropertiesFile.withInputStream { stream ->
+        localProperties.load(stream)
+    }
+}
+
+def flutterRoot = localProperties.getProperty('flutter.sdk')
+if (flutterRoot == null) {
+    throw new GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
+}
+
+apply plugin: 'com.android.application'
+apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
+
+android {
+    compileSdkVersion 28
+    
+
+    lintOptions {
+        disable 'InvalidPackage'
+    }
+
+    defaultConfig {
+        // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
+        applicationId "github.nisrulz.usingtabs"
+        minSdkVersion 16
+        targetSdkVersion 28
+        versionCode 1
+        versionName "1.0"
+        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
+    }
+
+    buildTypes {
+        release {
+            // TODO: Add your own signing config for the release build.
+            // Signing with the debug keys for now, so `flutter run --release` works.
+            signingConfig signingConfigs.debug
+        }
+    }
+}
+
+flutter {
+    source '../..'
+}
+
+dependencies {
+    androidTestImplementation 'com.android.support:support-annotations:28.0.0'
+    androidTestImplementation 'com.android.support.test:runner:1.0.2'
+    androidTestImplementation 'com.android.support.test:rules:1.0.2'
+}

case_study/memory_leak/android/app/src/main/AndroidManifest.xml

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+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="github.nisrulz.usingtabs">
+
+    <!-- The INTERNET permission is required for development. Specifically,
+         flutter needs it to communicate with the running application
+         to allow setting breakpoints, to provide hot reload, etc.
+    -->
+    <uses-permission android:name="android.permission.INTERNET"/>
+
+    <!-- io.flutter.app.FlutterApplication is an android.app.Application that
+         calls FlutterMain.startInitialization(this); in its onCreate method.
+         In most cases you can leave this as-is, but you if you want to provide
+         additional functionality it is fine to subclass or reimplement
+         FlutterApplication and put your custom class here. -->
+    <application android:name="io.flutter.app.FlutterApplication" android:label="using_tabs" android:icon="@mipmap/ic_launcher">
+        <activity android:name=".MainActivity"
+                  android:launchMode="singleTop"
+                  android:theme="@android:style/Theme.Black.NoTitleBar"
+                  android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|layoutDirection"
+                  android:hardwareAccelerated="true"
+                  android:windowSoftInputMode="adjustResize">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN"/>
+                <category android:name="android.intent.category.LAUNCHER"/>
+            </intent-filter>
+        </activity>
+    </application>
+</manifest>

case_study/memory_leak/android/app/src/main/java/github/nisrulz/usingtabs/MainActivity.java

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+package github.nisrulz.usingtabs;
+
+import android.os.Bundle;
+
+import io.flutter.app.FlutterActivity;
+import io.flutter.plugins.GeneratedPluginRegistrant;
+
+public class MainActivity extends FlutterActivity {
+  @Override
+  protected void onCreate(Bundle savedInstanceState) {
+    super.onCreate(savedInstanceState);
+    GeneratedPluginRegistrant.registerWith(this);
+  }
+}