Introduce tooling model for Android extensions plugin

Introduce Gradle models for plugins 'kotlin-android-extensions'.

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/BaseGradleIT.kt

@@ -284,7 +284,9 @@ abstract class BaseGradleIT {
 
         val connection = GradleConnector.newConnector().forProjectDirectory(projectDir).connect()
         val options = defaultBuildOptions()
-        val model = connection.action(ModelFetcherBuildAction(modelType)) .withArguments("-Pkotlin_version=" + options.kotlinVersion).run()
+        val arguments = mutableListOf("-Pkotlin_version=${options.kotlinVersion}")
+        options.androidGradlePluginVersion?.let { arguments.add("-Pandroid_tools_version=$it") }
+        val model = connection.action(ModelFetcherBuildAction(modelType)).withArguments(arguments).run()
         connection.close()
         return model
     }

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/model/KotlinAndroidExtensionIT.kt

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.gradle.model
+
+import org.jetbrains.kotlin.gradle.BaseGradleIT
+import org.jetbrains.kotlin.test.KotlinTestUtils
+import org.junit.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertNull
+import kotlin.test.assertTrue
+
+class KotlinAndroidExtensionIT : BaseGradleIT() {
+
+    override fun defaultBuildOptions(): BuildOptions {
+        return super.defaultBuildOptions().copy(
+            androidGradlePluginVersion = "3.0.0",
+            androidHome = KotlinTestUtils.findAndroidSdk()
+        )
+    }
+
+    @Test
+    fun testAndroidExtensionsProject() {
+        val project = Project("AndroidExtensionsProject")
+        val androidExtensionModel = project.getModels(KotlinAndroidExtension::class.java).getModel(":app")!!
+
+        assertEquals(1L, androidExtensionModel.modelVersion)
+        assertEquals("app", androidExtensionModel.name)
+        assertFalse(androidExtensionModel.isExperimental)
+        assertEquals("hashMap", androidExtensionModel.defaultCacheImplementation)
+    }
+
+    @Test
+    fun testAndroidExtensionsManyVariants() {
+        val project = Project("AndroidExtensionsManyVariants")
+        val androidExtensionModel = project.getModels(KotlinAndroidExtension::class.java).getModel(":app")!!
+
+        assertEquals(1L, androidExtensionModel.modelVersion)
+        assertEquals("app", androidExtensionModel.name)
+        assertTrue(androidExtensionModel.isExperimental)
+        assertEquals("hashMap", androidExtensionModel.defaultCacheImplementation)
+    }
+
+    @Test
+    fun testNonAndroidExtensionsProjects() {
+        val project = Project("kotlinProject")
+        val model = project.getModels(KotlinAndroidExtension::class.java).getModel(":")
+
+        assertNull(model)
+    }
+}