Rewire Android WebView's compositor changed signal.

android_webview/browser/test/rendering_test.cc

Index: android_webview/browser/test/rendering_test.cc
diff --git a/android_webview/browser/test/rendering_test.cc b/android_webview/browser/test/rendering_test.cc
index 1c92f34e98b05d64b3335cf9e75260e5680eed68..18b4629529cec3b58c0b0358cf51af533aec46f6 100644
--- a/android_webview/browser/test/rendering_test.cc
+++ b/android_webview/browser/test/rendering_test.cc
@@ -56,6 +56,7 @@ void RenderingTest::SetUpTestHarness() {
   DCHECK(!functor_.get());
   browser_view_renderer_.reset(
       new TestBrowserViewRenderer(this, base::ThreadTaskRunnerHandle::Get()));
+  browser_view_renderer_->SetActiveCompositorID(CompositorID(0, 0));
   InitializeCompositor();
   std::unique_ptr<FakeWindow> window(
       new FakeWindow(browser_view_renderer_.get(), this, gfx::Rect(100, 100)));