Introduce ReusableMainScope factory function

Author: DmitriyZaitsev

common/kotlinx-coroutines-core-common/src/CoroutineScope.kt

@@ -185,4 +185,8 @@ fun ReusableCoroutineScope(
 ): ReusableCoroutineScope =
     ReusableContextScope(if (context[Job] != null) context else context + newJob(), newJob)
 
+@Suppress("FunctionName")
+fun ReusableMainScope(): CoroutineScope =
+    ReusableContextScope(Dispatchers.Main) { SupervisorJob() }
+
 public val CoroutineScope.isReusable: Boolean get() = this is ReusableCoroutineScope

common/kotlinx-coroutines-core-common/test/CoroutineScopeTest.kt

@@ -323,6 +323,11 @@ class CoroutineScopeTest : TestBase() {
         assertTrue(reusableScope.isRestarted)
     }
 
+    @Test
+    fun testMainReusableScope() {
+        assertSame(ReusableMainScope().coroutineContext[ContinuationInterceptor], Dispatchers.Main)
+    }
+
     private fun scopePlusContext(c1: CoroutineContext, c2: CoroutineContext) =
         (ContextScope(c1) + c2).coroutineContext