Migrate MediaStream test code from content/shell/renderer/ to content/test/.

content/test/layouttest_support.cc

Index: content/test/layouttest_support.cc
diff --git a/content/test/layouttest_support.cc b/content/test/layouttest_support.cc
index 378e79d0998f8991488ed1c28e18c055561f5f56..19939173f0fc3fb05d6aa11d9413102165564a05 100644
--- a/content/test/layouttest_support.cc
+++ b/content/test/layouttest_support.cc
@@ -11,6 +11,7 @@
 #include "content/renderer/render_thread_impl.h"
 #include "content/renderer/render_view_impl.h"
 #include "content/renderer/renderer_webkitplatformsupport_impl.h"
+#include "content/test/test_media_stream_client.h"
 #include "third_party/WebKit/public/platform/WebGamepads.h"
 #include "third_party/WebKit/public/testing/WebFrameTestProxy.h"
 #include "third_party/WebKit/public/testing/WebTestProxy.h"
@@ -130,4 +131,10 @@ void DisableAutoResizeMode(RenderView* render_view, const WebSize& new_size) {
       ->DisableAutoResizeForTesting(new_size);
 }
 
+void UseMockMediaStreams(RenderView* render_view) {
+  RenderViewImpl* render_view_impl = static_cast<RenderViewImpl*>(render_view);
+  render_view_impl->SetMediaStreamClientForTesting(
+      new TestMediaStreamClient(render_view_impl));
+}
+
 }  // namespace content