Introduce frames control into Compose test API.

Several changes:
- Defragmented TestCase from benchmark into ComposeTestCase and
  AndroidTestCaseRunner and moved them to androidx.ui.testing. This
  enabled to introduce time controlled tests as part of regular compose
  testing API. We can also keep building on this to enable animations
  testing.
- Made hasPendingChanges to work again as part of time controlled tests.
  This will be particulary useful to bring in the regular testing APIs
  such as doClick, findByTag and others.
- Less boiler-plate when writing benchmarks thanks to
  ComposeBenchmarkRule.

Test: Added
Bug: b/122349846

Change-Id: Ie91d2854af48eb6799a1dc1f84fb0e4a1d5f8d02

diff --git a/ui/integration-tests/test/src/main/java/androidx/ui/test/cases/RectsInColumnSharedModelTestCase.kt b/ui/integration-tests/test/src/main/java/androidx/ui/test/cases/RectsInColumnSharedModelTestCase.kt
index 0dcf66c..c7ddc466 100644
--- a/ui/integration-tests/test/src/main/java/androidx/ui/test/cases/RectsInColumnSharedModelTestCase.kt
+++ b/ui/integration-tests/test/src/main/java/androidx/ui/test/cases/RectsInColumnSharedModelTestCase.kt

@@ -16,11 +16,9 @@
 
 package androidx.ui.test.cases
 
-import android.app.Activity
-import androidx.compose.FrameManager
+import androidx.compose.Composable
 import androidx.compose.Model
 import androidx.ui.core.dp
-import androidx.ui.core.setContent
 import androidx.ui.foundation.ColoredRect
 import androidx.ui.graphics.Color
 import androidx.ui.layout.Column
@@ -39,13 +37,13 @@
  * that the whole loop has to be re-run when model changes.
  */
 class RectsInColumnSharedModelTestCase(
-    activity: Activity,
     private val amountOfRectangles: Int
-) : ComposeTestCase(activity), ToggleableTestCase {
+) : ComposeTestCase, ToggleableTestCase {
 
     private val model = RectanglesInColumnTestCaseColorModel(Color.Black)
 
-    override fun setComposeContent(activity: Activity) = activity.setContent {
+    @Composable
+    override fun emitContent() {
         MaterialTheme {
             Column {
                 repeat(amountOfRectangles) { i ->
@@ -57,7 +55,7 @@
                 }
             }
         }
-    }!!
+    }
 
     override fun toggleState() {
         if (model.color == Color.Magenta) {
@@ -65,6 +63,5 @@
         } else {
             model.color = Color.Magenta
         }
-        FrameManager.nextFrame()
     }
 }
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