Kapt: Make javaCompile parameter in KotlinGradleSubplugin non-null

(cherry picked from commit 9686344)

libraries/examples/kotlin-gradle-subplugin-example/src/main/kotlin/example/ExampleSubplugin.kt

@@ -31,7 +31,7 @@ class ExampleSubplugin : KotlinGradleSubplugin {
     override fun apply(
             project: Project, 
             kotlinCompile: AbstractCompile, 
-            javaCompile: AbstractCompile?, 
+            javaCompile: AbstractCompile, 
             variantData: Any?,
             javaSourceSet: SourceSet?
     ): List<SubpluginOption> {

libraries/tools/kotlin-gradle-plugin-api/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinGradleSubplugin.kt

@@ -28,7 +28,7 @@ interface KotlinGradleSubplugin {
     fun apply(
             project: Project, 
             kotlinCompile: AbstractCompile, 
-            javaCompile: AbstractCompile?,
+            javaCompile: AbstractCompile,
             variantData: Any?,
             javaSourceSet: SourceSet?
     ): List<SubpluginOption>

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/internal/AndroidSubplugin.kt

@@ -62,7 +62,7 @@ class AndroidSubplugin : KotlinGradleSubplugin {
     override fun apply(
             project: Project,
             kotlinCompile: AbstractCompile, 
-            javaCompile: AbstractCompile?, 
+            javaCompile: AbstractCompile, 
             variantData: Any?, 
             javaSourceSet: SourceSet?
     ): List<SubpluginOption> {

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/internal/Kapt2KotlinGradleSubplugin.kt

@@ -61,8 +61,8 @@ class Kapt2KotlinGradleSubplugin : KotlinGradleSubplugin {
 
     override fun apply(
             project: Project, 
-            kotlinCompile: AbstractCompile, 
-            javaCompile: AbstractCompile?, 
+            kotlinCompile: AbstractCompile,
+            javaCompile: AbstractCompile,
             variantData: Any?,
             javaSourceSet: SourceSet?
     ): List<SubpluginOption> {

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinPlugin.kt

@@ -131,10 +131,8 @@ class Kotlin2JvmSourceSetProcessor(
 
                 val subpluginEnvironment = loadSubplugins(project)
                 subpluginEnvironment.addSubpluginArguments(project, kotlinTask, 
-                        javaTask as? AbstractCompile, null, sourceSet)
+                        javaTask as JavaCompile, null, sourceSet)
                 
-                if (javaTask !is JavaCompile) return@afterEvaluate
-
                 var kotlinAfterJavaTask: KotlinCompile? = null
 
                 if (aptConfiguration.dependencies.size > 1 && !Kapt2GradleSubplugin.isEnabled(project)) {
@@ -490,7 +488,7 @@ class SubpluginEnvironment(
     fun addSubpluginArguments(
             project: Project, 
             kotlinTask: KotlinCompile, 
-            javaTask: AbstractCompile?,
+            javaTask: AbstractCompile,
             variantData: Any?,
             javaSourceSet: SourceSet?) {
         val pluginOptions = kotlinTask.pluginOptions